Just the last line of the test failing:
2904:        Assert.assertEquals(1.f, imageControl.getCustomImageVisibilityPercentage(), 0);


I 1520.441s run_tests_on_device(HT74C0209082)  detected failure in org.chromium.chrome.browser.contextualsearch.ContextualSearchManagerTest#testQuickActionCaptionAndImage. raw output:
I 1520.441s run_tests_on_device(HT74C0209082)    INSTRUMENTATION_STATUS: numtests=1
I 1520.445s run_tests_on_device(HT74C0209082)    INSTRUMENTATION_STATUS: stream=
I 1520.445s run_tests_on_device(HT74C0209082)    org.chromium.chrome.browser.contextualsearch.ContextualSearchManagerTest:
I 1520.445s run_tests_on_device(HT74C0209082)    INSTRUMENTATION_STATUS: id=AndroidJUnitRunner
I 1520.445s run_tests_on_device(HT74C0209082)    INSTRUMENTATION_STATUS: test=testQuickActionCaptionAndImage
I 1520.445s run_tests_on_device(HT74C0209082)    INSTRUMENTATION_STATUS: class=org.chromium.chrome.browser.contextualsearch.ContextualSearchManagerTest
I 1520.445s run_tests_on_device(HT74C0209082)    INSTRUMENTATION_STATUS: current=1
I 1520.445s run_tests_on_device(HT74C0209082)    INSTRUMENTATION_STATUS_CODE: 1
I 1520.445s run_tests_on_device(HT74C0209082)    INSTRUMENTATION_STATUS: numtests=1
I 1520.446s run_tests_on_device(HT74C0209082)    INSTRUMENTATION_STATUS: stream=
I 1520.446s run_tests_on_device(HT74C0209082)    Error in testQuickActionCaptionAndImage(org.chromium.chrome.browser.contextualsearch.ContextualSearchManagerTest):
I 1520.446s run_tests_on_device(HT74C0209082)    java.lang.AssertionError: expected:<1.0> but was:<0.6739924>
I 1520.446s run_tests_on_device(HT74C0209082)    	at org.junit.Assert.fail(Assert.java:88)
I 1520.446s run_tests_on_device(HT74C0209082)    	at org.junit.Assert.failNotEquals(Assert.java:834)
I 1520.446s run_tests_on_device(HT74C0209082)    	at org.junit.Assert.assertEquals(Assert.java:575)
I 1520.446s run_tests_on_device(HT74C0209082)    	at org.junit.Assert.assertEquals(Assert.java:700)
I 1520.446s run_tests_on_device(HT74C0209082)    	at org.chromium.chrome.browser.contextualsearch.ContextualSearchManagerTest.testQuickActionCaptionAndImage(ContextualSearchManagerTest.java:2904)
I 1520.446s run_tests_on_device(HT74C0209082)    	at java.lang.reflect.Method.invoke(Native Method)
I 1520.447s run_tests_on_device(HT74C0209082)    	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
I 1520.447s run_tests_on_device(HT74C0209082)    	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
I 1520.447s run_tests_on_device(HT74C0209082)    	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:52)
I 1520.447s run_tests_on_device(HT74C0209082)    	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
I 1520.447s run_tests_on_device(HT74C0209082)    	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
I 1520.447s run_tests_on_device(HT74C0209082)    	at org.chromium.base.test.ScreenshotOnFailureStatement.evaluate(ScreenshotOnFailureStatement.java:37)
I 1520.447s run_tests_on_device(HT74C0209082)    	at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
I 1520.447s run_tests_on_device(HT74C0209082)    	at org.chromium.chrome.test.ChromeActivityTestRule$1.evaluate(ChromeActivityTestRule.java:113)
I 1520.447s run_tests_on_device(HT74C0209082)    	at android.support.test.internal.statement.UiThreadStatement.evaluate(UiThreadStatement.java:55)
I 1520.447s run_tests_on_device(HT74C0209082)    	at android.support.test.rule.ActivityTestRule$ActivityStatement.evaluate(ActivityTestRule.java:270)
I 1520.448s run_tests_on_device(HT74C0209082)    	at org.junit.rules.RunRules.evaluate(RunRules.java:20)
I 1520.448s run_tests_on_device(HT74C0209082)    	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
I 1520.448s run_tests_on_device(HT74C0209082)    	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
I 1520.448s run_tests_on_device(HT74C0209082)    	at org.chromium.base.test.BaseJUnit4ClassRunner.runChild(BaseJUnit4ClassRunner.java:201)
I 1520.448s run_tests_on_device(HT74C0209082)    	at org.chromium.base.test.BaseJUnit4ClassRunner.runChild(BaseJUnit4ClassRunner.java:43)
I 1520.448s run_tests_on_device(HT74C0209082)    	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
I 1520.448s run_tests_on_device(HT74C0209082)    	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
I 1520.448s run_tests_on_device(HT74C0209082)    	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
I 1520.448s run_tests_on_device(HT74C0209082)    	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
I 1520.448s run_tests_on_device(HT74C0209082)    	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
I 1520.448s run_tests_on_device(HT74C0209082)    	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
I 1520.448s run_tests_on_device(HT74C0209082)    	at org.chromium.base.test.BaseJUnit4ClassRunner.run(BaseJUnit4ClassRunner.java:183)
I 1520.449s run_tests_on_device(HT74C0209082)    	at org.junit.runners.Suite.runChild(Suite.java:128)
I 1520.449s run_tests_on_device(HT74C0209082)    	at org.junit.runners.Suite.runChild(Suite.java:27)
I 1520.449s run_tests_on_device(HT74C0209082)    	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
I 1520.449s run_tests_on_device(HT74C0209082)    	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
I 1520.449s run_tests_on_device(HT74C0209082)    	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
I 1520.449s run_tests_on_device(HT74C0209082)    	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
I 1520.449s run_tests_on_device(HT74C0209082)    	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
I 1520.449s run_tests_on_device(HT74C0209082)    	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
I 1520.449s run_tests_on_device(HT74C0209082)    	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
I 1520.450s run_tests_on_device(HT74C0209082)    	at org.junit.runner.JUnitCore.run(JUnitCore.java:115)
I 1520.450s run_tests_on_device(HT74C0209082)    	at android.support.test.internal.runner.TestExecutor.execute(TestExecutor.java:59)
I 1520.450s run_tests_on_device(HT74C0209082)    	at android.support.test.runner.AndroidJUnitRunner.onStart(AndroidJUnitRunner.java:262)
I 1520.450s run_tests_on_device(HT74C0209082)    	at org.chromium.base.test.BaseChromiumAndroidJUnitRunner.onStart(BaseChromiumAndroidJUnitRunner.java:103)
I 1520.450s run_tests_on_device(HT74C0209082)    	at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:2074)

Workaround applied.

The following revision WAS SUPPOSED TO refer to this bug:
------------------------------
  https://chromium.googlesource.com/chromium/src.git/+/84b690feb3f2e20883f72a5bcbfd141c65372a15

commit 84b690feb3f2e20883f72a5bcbfd141c65372a15
Author: Donn Denman <donnd@google.com>
Date: Wed Mar 07 02:06:10 2018

[TTS] Minor test cleanup and improvements.

Poll the UI thread instead of the Intrumentation thread
in some cases -- likely there are others that should be
changed too.

Remove my initials from test names (done for local
debugging and accidently submitted).

BUG=  818374  

Change-Id: I5bb80c520b155be94a9c1ecfc0c9c1f3a0e4184e
Reviewed-on: https://chromium-review.googlesource.com/950319
Reviewed-by: Theresa <twellington@chromium.org>
Commit-Queue: Donn Denman <donnd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#541282}
[modify] https://crrev.com/84b690feb3f2e20883f72a5bcbfd141c65372a15/chrome/android/javatests/src/org/chromium/chrome/browser/contextualsearch/ContextualSearchManagerTest.java
------------------------------