The current way of setting @CommandLindFlag as every test is surely not ideal.

My proposal on this is to similar to this CL: https://codereview.chromium.org/2523983002

Setting flags would be call `@Rule CommandLineTestRule mCommandLineRule = new CommandLineTestRule().setFlags(...)` but this doesn't resolve the maintenance load issue since every test still needs to set flag. But if we have a compound rule that wraps around other test rule, we can set the flags in the compound rule for every tests.

Have a look at my CL (https://chromium-review.googlesource.com/c/539563/)
and let me know what you think; either as an intermediate step to using
combined rules or as an alternative. I did wonder about combining rules,
but the only thing I can see that does this is RuleChain, and it wasn't
obvious to me that that would do what we want.

John has just added you as a reviewer of the CL, beating me to it by a few
seconds. Sorry I didn't do so in the first place.

Oh, not a problem at all: )

RuleChain works, but syntactically is rather annoying and are getting deprecated, most importantly, we probably want a custom way to make sure some rules run before others (e.g. CommandLineFlag before activity launch)

Reflectively searching for TestRule field is actually a pretty great way to resolve this issue!

Once the initial implementation of this has landed there we should move the existing common command line switches (e.g. DISABLE_FIRST_RUN_EXPERIENCE) to the appropriate rules (in this case ChromeActivityTestRule), and remove them from the tests. I don't propose to do this in the initial CL.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4b4ec5c8ec1ef6e2d76b116aae230ddec9b6451d

commit 4b4ec5c8ec1ef6e2d76b116aae230ddec9b6451d
Author: Anthony Berent <aberent@chromium.org>
Date: Thu Jun 22 16:55:35 2017

Enable CommandLineFlags annonations on Rules.

Enable CommandLineFlags.add and CommandLineFlags.remove on Junit4
Rules. The annotations are read in the order:
1. Annotations on Rule Classes and Rule Class Ancestors
2. Annotations on Test Class Ancestors
2. Annotations on Test Class
3  Annotations on Test method

Meaning that annotations on the test class or method can remove
command line flags set by rules.

The order in which annotations on different rules are applied is
undefined, but annotations on each rule's ancestors are read
before annotations on the rule itself

Note that if the @Rule annotation annotates a method (see
http://junit.org/junit4/javadoc/4.12/org/junit/Rule.html) then this
will only read CommandLine annotations on the formal return type of
the method, and not the actual type of the returned rule.

This CL also (as a test of this) adds command line flags to
BottomSheetTestRule, and removes them from tests using this rule.

BUG= 734553 

Change-Id: I1501cb6ca4ae3963775b299b1695304e471ac0ab
Reviewed-on: https://chromium-review.googlesource.com/539563
Commit-Queue: Anthony Berent <aberent@chromium.org>
Reviewed-by: John Budorick <jbudorick@chromium.org>
Reviewed-by: Yoland Yan <yolandyan@chromium.org>
Reviewed-by: Bernhard Bauer <bauerb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#481568}
[modify] https://crrev.com/4b4ec5c8ec1ef6e2d76b116aae230ddec9b6451d/base/test/android/javatests/src/org/chromium/base/test/util/CommandLineFlags.java
[modify] https://crrev.com/4b4ec5c8ec1ef6e2d76b116aae230ddec9b6451d/chrome/android/javatests/src/org/chromium/chrome/browser/appmenu/ChromeHomeAppMenuTest.java
[modify] https://crrev.com/4b4ec5c8ec1ef6e2d76b116aae230ddec9b6451d/chrome/android/javatests/src/org/chromium/chrome/browser/suggestions/SuggestionsBottomSheetTest.java
[modify] https://crrev.com/4b4ec5c8ec1ef6e2d76b116aae230ddec9b6451d/chrome/android/javatests/src/org/chromium/chrome/browser/suggestions/SuggestionsBottomSheetUiCaptureTest.java
[modify] https://crrev.com/4b4ec5c8ec1ef6e2d76b116aae230ddec9b6451d/chrome/android/javatests/src/org/chromium/chrome/browser/widget/bottomsheet/BottomSheetContentControllerTest.java
[modify] https://crrev.com/4b4ec5c8ec1ef6e2d76b116aae230ddec9b6451d/chrome/android/javatests/src/org/chromium/chrome/browser/widget/bottomsheet/BottomSheetObserverTest.java
[modify] https://crrev.com/4b4ec5c8ec1ef6e2d76b116aae230ddec9b6451d/chrome/test/android/javatests/src/org/chromium/chrome/test/BottomSheetTestRule.java
[modify] https://crrev.com/4b4ec5c8ec1ef6e2d76b116aae230ddec9b6451d/testing/android/docs/junit4.md