Add non-member non-mutating methods for common gfx::Rect operations.

ui/gfx/image/image_skia_operations.cc

Index: ui/gfx/image/image_skia_operations.cc
diff --git a/ui/gfx/image/image_skia_operations.cc b/ui/gfx/image/image_skia_operations.cc
index 029304b305ca5a9a954a79d1b3efdabf0a745fa5..a2395da148f767dd5da5d64811446d9fe74a1012 100644
--- a/ui/gfx/image/image_skia_operations.cc
+++ b/ui/gfx/image/image_skia_operations.cc
@@ -288,11 +288,9 @@ class ExtractSubsetImageSource: public gfx::ImageSkiaSource {
   // gfx::ImageSkiaSource overrides:
   virtual ImageSkiaRep GetImageForScale(ui::ScaleFactor scale_factor) OVERRIDE {
     ImageSkiaRep image_rep = image_.GetRepresentation(scale_factor);
-    gfx::RectF scaled_subset_bounds = subset_bounds_;
-    scaled_subset_bounds.Scale(
-        ui::GetScaleFactorScale(image_rep.scale_factor()));
-    SkIRect subset_bounds_in_pixel = RectToSkIRect(
-        ToFlooredRectDeprecated(scaled_subset_bounds));
+    float scale_to_pixel = ui::GetScaleFactorScale(image_rep.scale_factor());
+    SkIRect subset_bounds_in_pixel = RectToSkIRect(ToFlooredRectDeprecated(
+        gfx::ScaleRect(subset_bounds_, scale_to_pixel)));
     SkBitmap dst;
     bool success = image_rep.sk_bitmap().extractSubset(&dst,
                                                        subset_bounds_in_pixel);
@@ -432,8 +430,8 @@ ImageSkia ImageSkiaOperations::CreateButtonBackground(SkColor color,
 // static
 ImageSkia ImageSkiaOperations::ExtractSubset(const ImageSkia& image,
                                              const Rect& subset_bounds) {
-  gfx::Rect clipped_bounds = subset_bounds;
-  clipped_bounds.Intersect(gfx::Rect(image.size()));
+  gfx::Rect clipped_bounds =
+      gfx::IntersectRects(subset_bounds, gfx::Rect(image.size()));
   if (image.isNull() || clipped_bounds.IsEmpty()) {
     return ImageSkia();
   }