Merge 140035

Merge 140035
As approved in http://crbug.com/167028
> [chromium] Double-tap zoom should take into account accessibility fontScaleFactor
> https://bugs.webkit.org/show_bug.cgi?id=107123
> 
> Patch by John Mellor <johnme@chromium.org>; on 2013-01-17
> Reviewed by Adam Barth.
> 
> Platforms which support Text Autosizing (currently just Chrome for
> Android) may provide a textAutosizingFontScaleFactor (defaults to 1.0).
> 
> This value is intended to be chosen by the user to indicate how large
> they want text to appear, for example Chrome for Android has a "Text
> scaling" slider in Settings > Accessibility that lets you choose a value
> in the range 50% - 200% (defaults to 100%*).
> 
> For text in wide columns that typically gets autosized, this value is
> applied by multiplying the textAutosizingMultiplier computed for each
> cluster by the textAutosizingFontScaleFactor. Double-tap zoom will fit
> the column to the screen (ignoring the textAutosizingFontScaleFactor)
> since the column is wide. This part already works.
> 
> For text in narrow columns that doesn't get autosized, the
> textAutosizingFontScaleFactor is not applied through Text Autosizing,
> and instead needs to be applied by adjusting the double-tap zoom level.
> When double-tapping on narrow columns, instead of fitting the column to
> the screen (which would often zoom in excessively far), the existing
> logic in computeScaleAndScrollForHitRect applies a maximum zoom level
> called the legibleScale. This value needs to be multiplied by the
> textAutosizingFontScaleFactor, so that we zoom in proportionately
> further on non-autosized narrow columns, hence the effective text size
> (taking into account zoom) will have increased in proportion to the
> textAutosizingFontScaleFactor as expected.
> 
> * src/WebViewImpl.cpp:
> (WebKit::WebViewImpl::computeScaleAndScrollForHitRect):
>     Multiplies legibleScale (the maximum zoom level) by the
>     textAutosizingFontScaleFactor.
> * tests/WebFrameTest.cpp:
>     Added WebFrameTest.DivAutoZoomScaleFontScaleFactorTest based on
>     WebFrameTest.DivAutoZoomScaleBoundsTest to test the interaction
>     between textAutosizingFontScaleFactor and the double-tap zoom logic.
>     Also did minor cleanup to WebFrameTest.DivAutoZoomScaleBoundsTest.

TBR=commit-queue@webkit.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=140432