Add Blink support for showing image placeholders using range requests.

third_party/WebKit/Source/platform/graphics/PlaceholderImage.cpp

+// Copyright 2016 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 "platform/graphics/PlaceholderImage.h"
+
+#include "platform/geometry/FloatRect.h"
+#include "platform/graphics/Color.h"
+#include "platform/graphics/GraphicsContext.h"
+#include "platform/graphics/ImageObserver.h"
+#include "platform/graphics/paint/SkPictureBuilder.h"
+#include "third_party/skia/include/core/SkCanvas.h"
+#include "third_party/skia/include/core/SkColor.h"
+#include "third_party/skia/include/core/SkImage.h"
+#include "third_party/skia/include/core/SkPaint.h"
+#include "third_party/skia/include/core/SkPicture.h"
+#include "third_party/skia/include/core/SkRect.h"
+#include "third_party/skia/include/core/SkSize.h"
+
+namespace blink {
+
+namespace {
+
+// Gray with 40% opacity.
+const RGBA32 kFillColor = 0x66808080;
+
+}  // namespace
+
+PlaceholderImage::~PlaceholderImage() {}
+
+sk_sp<SkImage> PlaceholderImage::imageForCurrentFrame() {

[Stephen Chennney, 2016/10/17 18:09:17]

You're always creating a new image here, but my understanding is that this
method may be called over and over again so you should retain a handle to the
image you make, and only create it if the handle has not been created yet.

[sclittle, 2016/10/18 00:54:11]

Done.

+  const FloatRect destRect(0.0f, 0.0f, static_cast<float>(m_size.width()),
+                           static_cast<float>(m_size.height()));
+  SkPictureBuilder builder(destRect);
+  GraphicsContext& context = builder.context();
+  context.beginRecording(destRect);
+
+  context.setFillColor(kFillColor);
+  context.fillRect(destRect);
+
+  return SkImage::MakeFromPicture(
+      builder.endRecording(), SkISize::Make(m_size.width(), m_size.height()),
+      nullptr, nullptr);
+}
+
+void PlaceholderImage::draw(SkCanvas* canvas,
+                            const SkPaint& basePaint,
+                            const FloatRect& destRect,
+                            const FloatRect& srcRect,
+                            RespectImageOrientationEnum,
+                            ImageClampingMode) {
+  if (!srcRect.intersects(FloatRect(0.0f, 0.0f,
+                                    static_cast<float>(m_size.width()),
+                                    static_cast<float>(m_size.height())))) {
+    return;
+  }
+
+  SkPaint paint(basePaint);
+  paint.setStyle(SkPaint::kFill_Style);
+  paint.setColor(kFillColor);
+  canvas->drawRect(destRect, paint);
+
+  if (getImageObserver())
+    getImageObserver()->didDraw(this);
+}
+
+void PlaceholderImage::drawPattern(GraphicsContext& destContext,
+                                   const FloatRect& srcRect,
+                                   const FloatSize& scale,
+                                   const FloatPoint& phase,
+                                   SkXfermode::Mode compositeOp,
+                                   const FloatRect& destRect,
+                                   const FloatSize& repeatSpacing) {
+  Image::drawPattern(destContext, srcRect, scale, phase, compositeOp, destRect,
+                     repeatSpacing);
+
+  if (getImageObserver())
+    getImageObserver()->didDraw(this);
+}
+
+}  // namespace blink