The log is:
============
java.lang.AssertionError
	at org.chromium.base.test.util.TestFileUtil.deleteFile(TestFileUtil.java:55)
	at org.chromium.components.crash.browser.CrashDumpManagerTest.tearDown(CrashDumpManagerTest.java:40)
	at org.chromium.base.test.BaseTestResult.run(BaseTestResult.java:129)
	at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:191)
	at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:176)
	at android.test.InstrumentationTestRunner.onStart(InstrumentationTestRunner.java:554)
	at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:1701)
===============

The test was added recently by isherman@.

I am disabling the test, the CL is https://codereview.chromium.org/2902103004.

It looks like we're trying to delete all the files in the cache-directory - maybe there are files (or directories) in the cache-directory, that aren't cleaned before running this test?

Ilya: if it makes sense I think we should use a temporary directory for the tests instead of using the cache-directory directly.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/406f05e73b87ed54dd6b6ace45cea9385208c5ac

commit 406f05e73b87ed54dd6b6ace45cea9385208c5ac
Author: vitaliii <vitaliii@chromium.org>
Date: Wed May 24 15:08:26 2017

Disable CrashDumpManagerTest#testUploadMinidump_NullMinidumpPath (flaky)

TBR=gsennton@chromium.org,isherman@chromium.org

BUG=725379

Review-Url: https://codereview.chromium.org/2902103004
Cr-Commit-Position: refs/heads/master@{#474289}

[modify] https://crrev.com/406f05e73b87ed54dd6b6ace45cea9385208c5ac/components/crash/android/javatests/src/org/chromium/components/crash/browser/CrashDumpManagerTest.java

 Issue 726604  has been merged into this issue.

testUploadMinidump_NoCallback is also flaky (see  Issue 726604 ). Disabling and duping that bug into this.

Disable CL: https://chromium-review.googlesource.com/c/517003/

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/73fce28b25fd97073601ecb04ee5f88c16cc4ad2

commit 73fce28b25fd97073601ecb04ee5f88c16cc4ad2
Author: Matt Giuca <mgiuca@chromium.org>
Date: Fri May 26 07:44:45 2017

Disable CrashDumpManagerTest#testUploadMinidump_NoCallback (flaky).

TBR=gsennton@chromium.org,isherman@chromium.org

Bug: 725379
Change-Id: I20682c13346285b427b94f04300eb2056f0b5835
Reviewed-on: https://chromium-review.googlesource.com/517003
Reviewed-by: Matt Giuca <mgiuca@chromium.org>
Commit-Queue: Matt Giuca <mgiuca@chromium.org>
Cr-Commit-Position: refs/heads/master@{#474957}
[modify] https://crrev.com/73fce28b25fd97073601ecb04ee5f88c16cc4ad2/components/crash/android/javatests/src/org/chromium/components/crash/browser/CrashDumpManagerTest.java

 Issue 726976  has been merged into this issue.

 Issue 727506  has been merged into this issue.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6b0e73063c6d65e7172cd247e05006078a60cf23

commit 6b0e73063c6d65e7172cd247e05006078a60cf23
Author: isherman <isherman@chromium.org>
Date: Wed May 31 15:52:15 2017

Fix some flaky tests: Use a dedicated temp dir.

BUG=725379
TEST=CrashDumpManagerTest.*
R=gsennton@chromium.org

Review-Url: https://codereview.chromium.org/2911983008
Cr-Commit-Position: refs/heads/master@{#475924}

[modify] https://crrev.com/6b0e73063c6d65e7172cd247e05006078a60cf23/components/crash/android/javatests/src/org/chromium/components/crash/browser/CrashDumpManagerTest.java

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f6c031634d0e361e90534d410121d25c991b3a80

commit f6c031634d0e361e90534d410121d25c991b3a80
Author: pkasting <pkasting@chromium.org>
Date: Wed May 31 20:02:39 2017

Revert of Fix some flaky tests: Use a dedicated temp dir. (patchset #1 id:1 of https://codereview.chromium.org/2911983008/ )

Reason for revert:
Looks to be causing consistent failures on Android, e.g.:

https://luci-milo.appspot.com/buildbot/chromium.linux/Android%20Tests/42292

Original issue's description:
> Fix some flaky tests: Use a dedicated temp dir.
>
> BUG=725379
> TEST=CrashDumpManagerTest.*
> R=gsennton@chromium.org
>
> Review-Url: https://codereview.chromium.org/2911983008
> Cr-Commit-Position: refs/heads/master@{#475924}
> Committed: https://chromium.googlesource.com/chromium/src/+/6b0e73063c6d65e7172cd247e05006078a60cf23

TBR=gsennton@chromium.org,isherman@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=725379

Review-Url: https://codereview.chromium.org/2915883003
Cr-Commit-Position: refs/heads/master@{#475991}

[modify] https://crrev.com/f6c031634d0e361e90534d410121d25c991b3a80/components/crash/android/javatests/src/org/chromium/components/crash/browser/CrashDumpManagerTest.java

 Issue 726138  has been merged into this issue.

Hmm, I'm not sure why the revert in #14 was necessary -- that is, I'm not sure why these tests are still failing in some situations.  Gustav, any ideas?

I couldn't repro this on an O device.
The failures (at least here: https://chromium-swarm.appspot.com/task?id=3678480a2cb49510&refresh=10&show_raw=1 ) are running hammerheads on KTU84P (KitKat MR2), I'll flash one of those and see if I can repro.

I would say that the different failures here:
https://00e9e64bac2af4321a0dfa9ff8ca56d0e4f36a9588adea6da0-apidata.googleusercontent.com/download/storage/v1/b/chromium-result-details/o/html%2Fchrome_public_test_apk_Android%20Tests_42292_2017_05_31_T17_22_29-UTC?qk=AD5uMEvLa4a-rdo-67M3KerbsggFKuFZsjI7GuR5l6Nd4ttewrriTvZErrFz8AWxXvr6DI7mFMQeDI-RevS5-Hk_TK7v-ajPEFtYJ6WqZMhdgil88ZC91uccskLHx6UN1v8xlYCrOquDhbUcDbu6TnNY6Pf4ZHOAfMW8jgXzuKO6f-qEYkxx5wffbMr-wtHJLrT_axFonof3f2gPtA5NFJxDhnI-vuTsxJcEZak0td6_oD1BjsD8j8wZqejyeMh5Hs4Pr6lzEBfYvFZ6SViz7iQC_8RTYZcOtfeczVUV1ZmrA9JJkwdTSljbuNNO6JNVoEQ0YPXmj8Yg2KT8Y27FecCcH6AKJR5E2-m9XlJYbECFd0EdeCv9FLQVxUaBeuNkyxQcB8Gmw0oGuvpctKvNhKdwdVsZD7VO_NgQ6VFv6JVmJHXtgR2JAsXxm76vM1yYA-NArPV47d8rH2Qa4e1lCT564BK8CpbkS0hfyAU5TESd8JHbtL4f1_QI6yizQ9AfxejC6D_qXKp_ERhHUGk-IxVX1yU43iFFVguaawGMenYCfYGQHAGpakQrSbrktlg7fPM4sk2GTnjWEqcx2wKkZFmQRE5uO3grNQXq3EUhZ-7zasMhXll8PcS7HZIMASo144Tw43O8wulxZftBrOLczStQuf0kmFOVOIkORimD8lZHAuHBrRXZXuySyrcEDkr-bZJT7CENlk-GsWECSSMlZfpLG99LzKHJ-8ADwjymrzl5pBm-mOJ-egKygLZ9k81XL8xXjKZam6mB_HYDzWZ0zfON1Kp_5IbcHPpOlK5jVkpJn85QMss9r-zzBZBfD-AkZrSFLPkR7-wssmoItetIDEANDU6V8rSnQqCzqczF9h4xD728cy9Il9E


suggest that the temporary directory is never created.

java.io.IOException: open failed: ENOENT (No such file or directory)
	at java.io.File.createNewFile(File.java:946)
	at org.chromium.components.crash.browser.CrashDumpManagerTest.testUploadMinidump_MinidumpPathIsValid(CrashDumpManagerTest.java:99)
	at java.lang.reflect.Method.invokeNative(Native Method)
	at android.test.InstrumentationTestCase.runMethod(InstrumentationTestCase.java:214)
	at android.test.InstrumentationTestCase.runTest(InstrumentationTestCase.java:199)
	at org.chromium.base.test.BaseTestResult.run(BaseTestResult.java:129)
	at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:191)
	at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:176)
	at android.test.InstrumentationTestRunner.onStart(InstrumentationTestRunner.java:554)
	at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:1701)
Caused by: libcore.io.ErrnoException: open failed: ENOENT (No such file or directory)
	at libcore.io.Posix.open(Native Method)
	at libcore.io.BlockGuardOs.open(BlockGuardOs.java:110)
	at java.io.File.createNewFile(File.java:939)
	... 15 more


junit.framework.AssertionFailedError
	at org.chromium.components.crash.browser.CrashDumpManagerTest.testUploadMinidump_MinidumpPathIsDirectory(CrashDumpManagerTest.java:83)
	at java.lang.reflect.Method.invokeNative(Native Method)
	at android.test.InstrumentationTestCase.runMethod(InstrumentationTestCase.java:214)
	at android.test.InstrumentationTestCase.runTest(InstrumentationTestCase.java:199)
	at org.chromium.base.test.BaseTestResult.run(BaseTestResult.java:129)
	at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:191)
	at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:176)
	at android.test.InstrumentationTestRunner.onStart(InstrumentationTestRunner.java:554)
	at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:1701)



java.io.IOException: open failed: ENOENT (No such file or directory)
	at java.io.File.createNewFile(File.java:946)
	at org.chromium.components.crash.browser.CrashDumpManagerTest.testUploadMinidump_NoCallback(CrashDumpManagerTest.java:47)
	at java.lang.reflect.Method.invokeNative(Native Method)
	at android.test.InstrumentationTestCase.runMethod(InstrumentationTestCase.java:214)
	at android.test.InstrumentationTestCase.runTest(InstrumentationTestCase.java:199)
	at org.chromium.base.test.BaseTestResult.run(BaseTestResult.java:129)
	at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:191)
	at android.test.AndroidTestRunner.runTest(AndroidTestRunner.java:176)
	at android.test.InstrumentationTestRunner.onStart(InstrumentationTestRunner.java:554)
	at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:1701)
Caused by: libcore.io.ErrnoException: open failed: ENOENT (No such file or directory)
	at libcore.io.Posix.open(Native Method)
	at libcore.io.BlockGuardOs.open(BlockGuardOs.java:110)
	at java.io.File.createNewFile(File.java:939)
	... 15 more

Ran these tests on a hammerhead with KTU84P and repeated 20 times - the tests pass each time. I don't know what's different on the tryserver bots. Do we have a way of running these tests on those bots?

#20: try jobs :) but please don't kick a bunch of try jobs on linux_android_rel_ng

There are indeed other ways to run tests on the same hardware. I'll follow up off-thread; it's kinda complicated at the moment.

Detected 7 new flakes for test/step "org.chromium.components.crash.browser.CrashDumpManagerTest#testUploadMinidump_MinidumpPathIsDirectory". To see the actual flakes, please visit https://chromium-try-flakes.appspot.com/all_flake_occurrences?key=ahVzfmNocm9taXVtLXRyeS1mbGFrZXNycAsSBUZsYWtlImVvcmcuY2hyb21pdW0uY29tcG9uZW50cy5jcmFzaC5icm93c2VyLkNyYXNoRHVtcE1hbmFnZXJUZXN0I3Rlc3RVcGxvYWRNaW5pZHVtcF9NaW5pZHVtcFBhdGhJc0RpcmVjdG9yeQw. This message was posted automatically by the chromium-try-flakes app. Since flakiness is ongoing, the issue was moved back into Sheriff Bug Queue (unless already there).

I agree that it seems the temp directory is failing to be created.  I'm not sure what might cause that -- file permissions? Full disk?

Thanks for helping to investigate!  Please include me on off-thread discussion as well -- if nothing else, I might learn something =)

Not a trooper bug, fwiw. Writing up the instructions now.

Ugh, I just realized that the bot pkasting@ is referring to (that's failing with Ilya's CL) is 'Android Tests' on 'chromium.linux'. John, is it OK to use your instructions on that builder? (I tried running on linux_android_rel_ng / tryserver.chromium.android and that run succeeds).

Or is it possible to see runs from 31st of May for linux_android_rel_ng?
From here:
https://build.chromium.org/p/tryserver.chromium.android/builders/linux_android_rel_ng
I can only see the 200 most recent runs, and that's not enough to see results from when Ilya landed his CL.

#26: Yeah, that uses the same devices (hammerhead/KTU84P) as linux_android_rel_ng.

#27: Again, I'll follow up offline.

Detected 3 new flakes for test/step "org.chromium.components.crash.browser.CrashDumpManagerTest#testUploadMinidump_MinidumpPathIsDirectory". To see the actual flakes, please visit https://chromium-try-flakes.appspot.com/all_flake_occurrences?key=ahVzfmNocm9taXVtLXRyeS1mbGFrZXNycAsSBUZsYWtlImVvcmcuY2hyb21pdW0uY29tcG9uZW50cy5jcmFzaC5icm93c2VyLkNyYXNoRHVtcE1hbmFnZXJUZXN0I3Rlc3RVcGxvYWRNaW5pZHVtcF9NaW5pZHVtcFBhdGhJc0RpcmVjdG9yeQw. This message was posted automatically by the chromium-try-flakes app. Since flakiness is ongoing, the issue was moved back into Sheriff Bug Queue (unless already there).

https://chromium-review.googlesource.com/c/524042/ is out to disable the remaining tests.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/119740b795871b7c4fc374c3e13d15ebf20ced4f

commit 119740b795871b7c4fc374c3e13d15ebf20ced4f
Author: Colin Blundell <blundell@chromium.org>
Date: Mon Jun 05 09:51:28 2017

Disable remaining CrashDumpManager tests due to flake

At least one of these tests continues to exhibit flake, and there's no
reason to suppose that the other isn't subject to the same problems as
the rest of the tests in this suite, as it looks like it's going
through the same basic flow.

TBR=isherman@chromium.org

Bug: 725379
Change-Id: I1fa0747d9554e64b67f4c6ee11777d9096ff5572
Reviewed-on: https://chromium-review.googlesource.com/524042
Reviewed-by: Colin Blundell <blundell@chromium.org>
Commit-Queue: Colin Blundell <blundell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#476964}
[modify] https://crrev.com/119740b795871b7c4fc374c3e13d15ebf20ced4f/components/crash/android/javatests/src/org/chromium/components/crash/browser/CrashDumpManagerTest.java

According to the flakiness dashboard these tests did fail a couple of times when run using swarming:

https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=chrome_public_test_apk&tests=testUploadMinidump
just after Ilya's CL landed. AFAICT they failed consistently (2/2 times) until pkasting@ landed the revert.