Add line height setting to views::Label & use it for notifications.

ui/gfx/canvas.h

Index: ui/gfx/canvas.h
diff --git a/ui/gfx/canvas.h b/ui/gfx/canvas.h
index c7673bccd24ba8612ccbd17f76f3974d22d1bd89..031b99a02fac4b5dea16a7cd6ed1a54b218382c9 100644
--- a/ui/gfx/canvas.h
+++ b/ui/gfx/canvas.h
@@ -128,6 +128,7 @@ class UI_EXPORT Canvas {
   static void SizeStringInt(const string16& text,
                             const gfx::Font& font,
                             int* width, int* height,
+                            int line_height,  // Only on SKIA and -1 = default.
                             int flags);
 
   // Returns the number of horizontal pixels needed to display the specified
@@ -327,6 +328,7 @@ class UI_EXPORT Canvas {
                              const gfx::Font& font,
                              SkColor color,
                              const gfx::Rect& text_bounds,
+                             int line_height,  // Only on SKIA and -1 = default.
                              int flags,
                              const ShadowValues& shadows);