ui: Eliminate allocating gfx::Canvas on the heap for every view.

ui/gfx/canvas.cc

 // 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 "ui/gfx/canvas.h"
 
 #include <cmath>
 #include <limits>
 
 #include "base/i18n/rtl.h"
 #include "base/logging.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "third_party/skia/include/effects/SkGradientShader.h"
 #include "ui/gfx/font_list.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/rect_conversions.h"
 #include "ui/gfx/geometry/safe_integer_conversions.h"
 #include "ui/gfx/geometry/size_conversions.h"
 #include "ui/gfx/scoped_canvas.h"
 #include "ui/gfx/skia_util.h"
 #include "ui/gfx/transform.h"
 
 #if defined(OS_WIN)
 #include "ui/gfx/canvas_skia_paint.h"

[danakj, 2015/05/11 23:42:53]

Oops, included a rebase here, not part of my changes.

 #endif
 
 namespace gfx {
 
 Canvas::Canvas(const Size& size, float image_scale, bool is_opaque)
     : image_scale_(image_scale),
       canvas_(NULL) {
   Size pixel_size = ToCeiledSize(ScaleSize(size, image_scale));
   owned_canvas_ = skia::AdoptRef(skia::CreatePlatformCanvas(pixel_size.width(),
                                                             pixel_size.height(),
@@ skipping 21 matching lines @@
   canvas_->scale(scale_scalar, scale_scalar);
   DrawImageInt(ImageSkia(image_rep), 0, 0);
 }
 
 Canvas::Canvas()
     : image_scale_(1.0),
       owned_canvas_(skia::AdoptRef(skia::CreatePlatformCanvas(0, 0, false))),
       canvas_(owned_canvas_.get()) {
 }
 
+Canvas::Canvas(SkCanvas* canvas, float image_scale)
+    : image_scale_(image_scale), owned_canvas_(), canvas_(canvas) {
+  DCHECK(canvas);
+}
+
 Canvas::~Canvas() {
 }
 
-// static
-Canvas* Canvas::CreateCanvasWithoutScaling(SkCanvas* canvas,
-                                           float image_scale) {
-  return new Canvas(canvas, image_scale);
-}
-
 void Canvas::RecreateBackingCanvas(const Size& size,
                                    float image_scale,
                                    bool is_opaque) {
   image_scale_ = image_scale;
   Size pixel_size = ToFlooredSize(ScaleSize(size, image_scale));
   owned_canvas_ = skia::AdoptRef(skia::CreatePlatformCanvas(pixel_size.width(),
                                                             pixel_size.height(),
                                                             is_opaque));
   canvas_ = owned_canvas_.get();
   SkScalar scale_scalar = SkFloatToScalar(image_scale);
@@ skipping 456 matching lines @@
 }
 
 void Canvas::EndPlatformPaint() {
   skia::EndPlatformPaint(canvas_);
 }
 
 void Canvas::Transform(const gfx::Transform& transform) {
   canvas_->concat(transform.matrix());
 }
 
-Canvas::Canvas(SkCanvas* canvas, float image_scale)
-    : image_scale_(image_scale),
-      owned_canvas_(),
-      canvas_(canvas) {
-  DCHECK(canvas);
-}
-
 bool Canvas::IntersectsClipRectInt(int x, int y, int w, int h) {
   SkRect clip;
   return canvas_->getClipBounds(&clip) &&
       clip.intersect(SkIntToScalar(x), SkIntToScalar(y), SkIntToScalar(x + w),
                      SkIntToScalar(y + h));
 }
 
 bool Canvas::IntersectsClipRect(const Rect& rect) {
   return IntersectsClipRectInt(rect.x(), rect.y(),
                                rect.width(), rect.height());
@@ skipping 65 matching lines @@
   // by the paint).
   SkPaint p(paint);
   p.setFilterQuality(filter ? kLow_SkFilterQuality : kNone_SkFilterQuality);
   p.setShader(shader.get());
 
   // The rect will be filled by the bitmap.
   canvas_->drawRect(dest_rect, p);
 }
 
 }  // namespace gfx