Set the antialiasing flag in the SkPaint structure used by the RenderTextHarfBuzz class before querying the font metrics from skia.

This ensures that skia does not return GDI compatible metrics from DirectWrite. The other change is to set the text size
in the PlatformFontWin::CreateHFontRefFromSkia function in the SkPaint structure used for querying the font metrics from
skia.

The DirectWrite version of this function multiplies the text size with the DirectWrite metrics which ensures that the
correct metrics are returned. This is noticeable in the omnibox where the text is not centered.

The other change is to calculate the average character width using the text extents API. The GetDluBasX function
has code to do this. Refactored into a helper function GetAverageCharWidthInDialogUnits and used that from the
CreateHFontRefFromSkia function. This is needed because width of some widgets like FindBar etc relies on the
character width containing a valid value. DirectWrite does not provide it in the metrics functions. Needs some investigation.

BUG=389649, 431917

Review URL: https://codereview.chromium.org/703613005

Cr-Commit-Position: refs/heads/master@{#303727}

1 files changed, 4 insertions, 0 deletions

diff --git a/ui/gfx/platform_font_win.h b/ui/gfx/platform_font_win.h
index eaed10c..483dc89 100644
--- a/ui/gfx/platform_font_win.h
+++ b/ui/gfx/platform_font_win.h
@@ -112,6 +112,10 @@ class GFX_EXPORT PlatformFontWin : public PlatformFont {
     // Returns the average character width in dialog units.
     int GetDluBaseX();
 
+    // Helper to return the average character width using the text extent
+    // technique mentioned here. http://support.microsoft.com/kb/125681.
+    static int GetAverageCharWidthInDialogUnits(HFONT gdi_font);
+
    private:
     friend class base::RefCounted<HFontRef>;
     FRIEND_TEST_ALL_PREFIXES(RenderTextTest, HarfBuzz_UniscribeFallback);