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

ui/gfx/canvas.cc

Index: ui/gfx/canvas.cc
diff --git a/ui/gfx/canvas.cc b/ui/gfx/canvas.cc
index 134c1453d2e104d7351b7abcd87f08ed215a2b3a..e54201dbd2308ffc73026147603e829f03a18b9d 100644
--- a/ui/gfx/canvas.cc
+++ b/ui/gfx/canvas.cc
@@ -89,7 +89,7 @@ void Canvas::RecreateBackingCanvas(const gfx::Size& size,
 // static
 int Canvas::GetStringWidth(const string16& text, const gfx::Font& font) {
   int width = 0, height = 0;
-  Canvas::SizeStringInt(text, font, &width, &height, NO_ELLIPSIS);
+  Canvas::SizeStringInt(text, font, &width, &height, -1, NO_ELLIPSIS);
   return width;
 }
 
@@ -433,6 +433,7 @@ void Canvas::DrawStringInt(const string16& text,
                         font,
                         color,
                         gfx::Rect(x, y, w, h),
+                        -1,  // Default line height.
                         flags,
                         ShadowValues());
 }