Merge 249331 "Tab close buttons can only be targeted with touch ..."

Merge 249331 "Tab close buttons can only be targeted with touch ..."

This change will resolve issue 332334 in branch 1750 (M33) and will
also prevent the regression described in issue 338516. See
comment 92 in issue 332334 for a full description.

> Tab close buttons can only be targeted with touch if the whole button is visible
> 
> As a result of r246686 landing, tabs can be too easy to close with
> touch in stacked tab mode when rect-based targeting is enabled.
> This patch changes the behaviour so that:
> 
> (1) Hit tests in response to a mouse event will always consider the
>     region of the tab close button that is visible.
> (2) Hit tests in response to a gesture will only consider the tab
>     close button to be a valid target if the entire button is
>     visible to the user.
> 
> Note that if there is any vertical clipping of the tab
> close button, we do not consider the clipped
> region to be a part of the button's bounds.
> 
> BUG=338516, 332334
> TEST=TabStripTest.ClippedTabCloseButton, also manually tested on Windows when tab close buttons are vertically clipped
> 
> Review URL: https://codereview.chromium.org/147623004

TBR=tdanderson@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=250156

[tdanderson, 2014-02-10 18:24:30]

Committed patchset #1 manually as r250156.