The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7ffeb9cc2f206d63942c7e6cf56037d5e26046a8

commit 7ffeb9cc2f206d63942c7e6cf56037d5e26046a8
Author: Jinsuk Kim <jinsukkim@chromium.org>
Date: Thu Jul 20 00:36:02 2017

Fix WebappModeTest.testWebappRequiresValidMac

The test passes fine on the release build but shows flakiness on
the debug build whose trybot result I'm trying to stablize. It
takes a bit longer to get the test page fully loaded on the debug
build, therefore the test often timed out before proceeding to
the next step. This CL ensures the scale factor gets matched
by waiting for the tab to be created before the test is performed. 
Local tests shows 100% pass, compared to about 50% failures before
the patch.

BUG=737910, 746476

Change-Id: If270b2c5dba122c899cba0f050ca808878773048
Reviewed-on: https://chromium-review.googlesource.com/559330
Reviewed-by: Tommy Nyquist <nyquist@chromium.org>
Reviewed-by: Changwan Ryu <changwan@chromium.org>
Commit-Queue: Jinsuk Kim <jinsukkim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#488063}
[modify] https://crrev.com/7ffeb9cc2f206d63942c7e6cf56037d5e26046a8/chrome/android/javatests/src/org/chromium/chrome/browser/TabsOpenedFromExternalAppTest.java
[modify] https://crrev.com/7ffeb9cc2f206d63942c7e6cf56037d5e26046a8/chrome/test/android/javatests/src/org/chromium/chrome/test/MultiActivityTestBase.java
[modify] https://crrev.com/7ffeb9cc2f206d63942c7e6cf56037d5e26046a8/chrome/test/android/javatests/src/org/chromium/chrome/test/MultiActivityTestCommon.java
[modify] https://crrev.com/7ffeb9cc2f206d63942c7e6cf56037d5e26046a8/chrome/test/android/javatests/src/org/chromium/chrome/test/MultiActivityTestRule.java
[modify] https://crrev.com/7ffeb9cc2f206d63942c7e6cf56037d5e26046a8/chrome/test/android/javatests/src/org/chromium/chrome/test/util/ApplicationTestUtils.java