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

content/browser/renderer_host/render_widget_host_view_mac.mm

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/renderer_host/render_widget_host_view_mac.h"
 
 #include <QuartzCore/QuartzCore.h>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 834 matching lines @@
   if (!output->Allocate(
       dst_pixel_size.width(), dst_pixel_size.height(), true))
     return;
   scoped_callback_runner.Release();
 
   // Convert |src_subrect| from the views coordinate (upper-left origin) into
   // the OpenGL coordinate (lower-left origin).
   gfx::Rect src_gl_subrect = src_subrect;
   src_gl_subrect.set_y(GetViewBounds().height() - src_subrect.bottom());
 
-  gfx::Rect src_pixel_gl_subrect =
-      gfx::ToEnclosingRect(src_gl_subrect.Scale(scale));
+  gfx::RectF scaled_src_gl_subrect = src_gl_subrect;
+  scaled_src_gl_subrect.Scale(scale);
+  gfx::Rect src_pixel_gl_subrect = gfx::ToEnclosingRect(scaled_src_gl_subrect);
   compositing_iosurface_->CopyTo(
       src_pixel_gl_subrect,
       dst_pixel_size,
       output->GetBitmap().getPixels(),
       callback);
 }
 
 // Sets whether or not to accept first responder status.
 void RenderWidgetHostViewMac::SetTakesFocusOnlyOnMouseDown(bool flag) {
   [cocoa_view_ setTakesFocusOnlyOnMouseDown:flag];
@@ skipping 244 matching lines @@
     }
   }
 
   size_t end_idx;
   if (!GetLineBreakIndex(composition_bounds_, range, &end_idx)) {
     end_idx = range.end();
   }
   *actual_range = ui::Range(range.start(), end_idx);
   gfx::Rect rect = composition_bounds_[range.start()];
   for (size_t i = range.start() + 1; i < end_idx; ++i) {
-    rect = rect.Union(composition_bounds_[i]);
+    rect.Union(composition_bounds_[i]);
   }
   return rect;
 }
 
 ui::Range RenderWidgetHostViewMac::ConvertCharacterRangeToCompositionRange(
     const ui::Range& request_range) {
   if (composition_range_.is_empty())
     return ui::Range::InvalidRange();
 
   if (request_range.is_reversed())
@@ skipping 1130 matching lines @@
     // Note: All coordinates are in view units, not pixels.
     gfx::Rect bitmapRect(0, 0,
                          backingStore->size().width(),
                          backingStore->size().height());
 
     // Specify the proper y offset to ensure that the view is rooted to the
     // upper left corner.  This can be negative, if the window was resized
     // smaller and the renderer hasn't yet repainted.
     int yOffset = NSHeight([self bounds]) - backingStore->size().height();
 
-    gfx::Rect paintRect = bitmapRect.Intersect(damagedRect);
+    gfx::Rect paintRect = bitmapRect;
+    paintRect.Intersect(damagedRect);
     if (!paintRect.IsEmpty()) {
       // if we have a CGLayer, draw that into the window
       if (backingStore->cg_layer()) {
         CGContextRef context = static_cast<CGContextRef>(
             [[NSGraphicsContext currentContext] graphicsPort]);
 
         // TODO: add clipping to dirtyRect if it improves drawing performance.
         CGContextDrawLayerAtPoint(context, CGPointMake(0.0, yOffset),
                                   backingStore->cg_layer());
       } else {
@@ skipping 1014 matching lines @@
   if (!string) return NO;
 
   // If the user is currently using an IME, confirm the IME input,
   // and then insert the text from the service, the same as TextEdit and Safari.
   [self confirmComposition];
   [self insertText:string];
   return YES;
 }
 
 @end