Make gfx::Rect class operations consistently mutate the class they are called on.

content/renderer/browser_plugin/browser_plugin_backing_store.cc

Index: content/renderer/browser_plugin/browser_plugin_backing_store.cc
diff --git a/content/renderer/browser_plugin/browser_plugin_backing_store.cc b/content/renderer/browser_plugin/browser_plugin_backing_store.cc
index e29d5b319d18a3e8e70472140026f0adf01e161f..131b0d097be594d5efe5be3569e34c1690249e99 100644
--- a/content/renderer/browser_plugin/browser_plugin_backing_store.cc
+++ b/content/renderer/browser_plugin/browser_plugin_backing_store.cc
@@ -37,8 +37,9 @@ void BrowserPluginBackingStore::PaintToBackingStore(
   if (bitmap_rect.IsEmpty())
     return;
 
-  gfx::Rect pixel_bitmap_rect =
-      gfx::ToEnclosingRect(bitmap_rect.Scale(scale_factor_));
+  gfx::RectF scaled_bitmap_rect = bitmap_rect;
+  scaled_bitmap_rect.Scale(scale_factor_);
+  gfx::Rect pixel_bitmap_rect = gfx::ToEnclosingRect(scaled_bitmap_rect);
 
   const int width = pixel_bitmap_rect.width();
   const int height = pixel_bitmap_rect.height();
@@ -57,8 +58,9 @@ void BrowserPluginBackingStore::PaintToBackingStore(
   sk_bitmap.setConfig(SkBitmap::kARGB_8888_Config, width, height);
   sk_bitmap.setPixels(dib->memory());
   for (size_t i = 0; i < copy_rects.size(); i++) {
-    const gfx::Rect& pixel_copy_rect =
-        gfx::ToEnclosingRect(copy_rects[i].Scale(scale_factor_));
+    gfx::RectF scaled_copy_rect = copy_rects[i];
+    scaled_copy_rect.Scale(scale_factor_);
+    const gfx::Rect& pixel_copy_rect = gfx::ToEnclosingRect(scaled_copy_rect);
     int x = pixel_copy_rect.x() - pixel_bitmap_rect.x();
     int y = pixel_copy_rect.y() - pixel_bitmap_rect.y();
     SkIRect srcrect = SkIRect::MakeXYWH(x, y,
@@ -79,7 +81,9 @@ void BrowserPluginBackingStore::ScrollBackingStore(
     int dy,
     const gfx::Rect& clip_rect,
     const gfx::Size& view_size) {
-  gfx::Rect pixel_rect = gfx::ToEnclosingRect(clip_rect.Scale(scale_factor_));
+  gfx::RectF scaled_clip_rect = clip_rect;
+  scaled_clip_rect.Scale(scale_factor_);
+  gfx::Rect pixel_rect = gfx::ToEnclosingRect(scaled_clip_rect);
   int pixel_dx = dx * scale_factor_;
   int pixel_dy = dy * scale_factor_;