I've only refined behavior for the cases when src/dst rect is empty.

Sorry I don't work on Chrome anymore.

Assigning to RWHVAndroid owner for further triage/assignment.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/caa6a6165d28c3bb499fc0aec9bf391c6bda1578

commit caa6a6165d28c3bb499fc0aec9bf391c6bda1578
Author: miu <miu@chromium.org>
Date: Wed Mar 08 23:36:06 2017

Fix Android tab navigation "stretch" regression.

Fixes a regression in the tab-switching UI caused by
https://codereview.chromium.org/2702093002. The root cause was my
misunderstanding of the difference between RenderWidgtHostViewAndroid's
|current_frame_size_| and the "view size" value returned by
ContentViewCoreImpl.

Note: While this change fixes the regression, there still seems to be a
small (~2 pixel) width-stretching problem (barely noticeable). However,
I confirmed that behavior is the same on current Clank stable; so, this
isn't related to the bug at-hand. Something to look into later...

This change revisits all code paths leading to CopyFromSurface() on
Android, and fixes a few other pre-existing issues:

1. RWHVAndroid::GetScaledContentBitmap(), was substituting
|current_surface_size_| instead of ContentViewCore::GetViewSize() when
the source rect argument is empty. This is actually the same bug that I
fixed above to resolve the regression. ;-)

2. RWHVAndroid::SynchronousCopyContents() does not copy the correct
source region if the rect's origin is not at the point (0,0).

3. The plumbing from CustomTabObserver (Java code) into the eventual
RWHVA::CopyFromSurface() was simplified.

BUG=698157, 698974 
TEST=Manually tested on Nexus 6, per bug repro steps.

Review-Url: https://codereview.chromium.org/2734043003
Cr-Commit-Position: refs/heads/master@{#455595}

[modify] https://crrev.com/caa6a6165d28c3bb499fc0aec9bf391c6bda1578/chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java
[modify] https://crrev.com/caa6a6165d28c3bb499fc0aec9bf391c6bda1578/chrome/android/java/src/org/chromium/chrome/browser/customtabs/CustomTabObserver.java
[modify] https://crrev.com/caa6a6165d28c3bb499fc0aec9bf391c6bda1578/content/browser/renderer_host/render_widget_host_view_android.cc
[modify] https://crrev.com/caa6a6165d28c3bb499fc0aec9bf391c6bda1578/content/browser/renderer_host/render_widget_host_view_android.h
[modify] https://crrev.com/caa6a6165d28c3bb499fc0aec9bf391c6bda1578/content/browser/web_contents/web_contents_android.cc
[modify] https://crrev.com/caa6a6165d28c3bb499fc0aec9bf391c6bda1578/content/browser/web_contents/web_contents_android.h
[modify] https://crrev.com/caa6a6165d28c3bb499fc0aec9bf391c6bda1578/content/public/android/java/src/org/chromium/content/browser/webcontents/WebContentsImpl.java
[modify] https://crrev.com/caa6a6165d28c3bb499fc0aec9bf391c6bda1578/content/public/android/java/src/org/chromium/content_public/browser/WebContents.java

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ad1ad1825e9b3190cbc399ab868f25eb3f50997f

commit ad1ad1825e9b3190cbc399ab868f25eb3f50997f
Author: Yuri Wiitala <miu@chromium.org>
Date: Fri Mar 10 23:45:08 2017

Fix Android tab navigation "stretch" regression.

Fixes a regression in the tab-switching UI caused by
https://codereview.chromium.org/2702093002. The root cause was my
misunderstanding of the difference between RenderWidgtHostViewAndroid's
|current_frame_size_| and the "view size" value returned by
ContentViewCoreImpl.

Note: While this change fixes the regression, there still seems to be a
small (~2 pixel) width-stretching problem (barely noticeable). However,
I confirmed that behavior is the same on current Clank stable; so, this
isn't related to the bug at-hand. Something to look into later...

This change revisits all code paths leading to CopyFromSurface() on
Android, and fixes a few other pre-existing issues:

1. RWHVAndroid::GetScaledContentBitmap(), was substituting
|current_surface_size_| instead of ContentViewCore::GetViewSize() when
the source rect argument is empty. This is actually the same bug that I
fixed above to resolve the regression. ;-)

2. RWHVAndroid::SynchronousCopyContents() does not copy the correct
source region if the rect's origin is not at the point (0,0).

3. The plumbing from CustomTabObserver (Java code) into the eventual
RWHVA::CopyFromSurface() was simplified.

BUG=698157, 698974 
TEST=Manually tested on Nexus 6, per bug repro steps.

Review-Url: https://codereview.chromium.org/2734043003
Cr-Commit-Position: refs/heads/master@{#455595}
(cherry picked from commit caa6a6165d28c3bb499fc0aec9bf391c6bda1578)

Review-Url: https://codereview.chromium.org/2741993004 .
Cr-Commit-Position: refs/branch-heads/3029@{#127}
Cr-Branched-From: 939b32ee5ba05c396eef3fd992822fcca9a2e262-refs/heads/master@{#454471}

[modify] https://crrev.com/ad1ad1825e9b3190cbc399ab868f25eb3f50997f/chrome/android/java/src/org/chromium/chrome/browser/ChromeActivity.java
[modify] https://crrev.com/ad1ad1825e9b3190cbc399ab868f25eb3f50997f/chrome/android/java/src/org/chromium/chrome/browser/customtabs/CustomTabObserver.java
[modify] https://crrev.com/ad1ad1825e9b3190cbc399ab868f25eb3f50997f/content/browser/renderer_host/render_widget_host_view_android.cc
[modify] https://crrev.com/ad1ad1825e9b3190cbc399ab868f25eb3f50997f/content/browser/renderer_host/render_widget_host_view_android.h
[modify] https://crrev.com/ad1ad1825e9b3190cbc399ab868f25eb3f50997f/content/browser/web_contents/web_contents_android.cc
[modify] https://crrev.com/ad1ad1825e9b3190cbc399ab868f25eb3f50997f/content/browser/web_contents/web_contents_android.h
[modify] https://crrev.com/ad1ad1825e9b3190cbc399ab868f25eb3f50997f/content/public/android/java/src/org/chromium/content/browser/webcontents/WebContentsImpl.java
[modify] https://crrev.com/ad1ad1825e9b3190cbc399ab868f25eb3f50997f/content/public/android/java/src/org/chromium/content_public/browser/WebContents.java

The limitation is documented in a comment, and that's probably enough for now.  If/when a use case arises for the positioned subrect readback, whoever works on that feature can add the capability.