Clamp the max size of fonts used by skia/chrome canvas.

app/gfx/font.h

Index: app/gfx/font.h
diff --git a/app/gfx/font.h b/app/gfx/font.h
index f79f6d060d99005e0f2637e9371e000fb25842ee..550c59d13ceca85d958a54659cbc00f2b9baa2f0 100644
--- a/app/gfx/font.h
+++ b/app/gfx/font.h
@@ -219,6 +219,10 @@ class Font {
   // The default font, used for the default constructor.
   static Font* default_font_;
 
+  // Return the scale factor for fonts that account for DPI.  We clamp the
+  // max DPI to prevent large fonts from overflowing UI elements.
+  static float GetPangoScaleFactor();
+
   // The average width of a character, initialized and cached if needed.
   double avg_width() const;