[WIP] Adding support for <iframe>s to slimming paint.

Source/core/paint/TranslationRecorder.cpp

+// Copyright 2014 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 "config.h"
+#include "core/paint/TranslationRecorder.h"
+
+#include "platform/RuntimeEnabledFeatures.h"
+#include "platform/graphics/GraphicsContext.h"
+
+namespace blink {
+
+void TranslationDisplayItem::replay(GraphicsContext* context)

[chrishtr, 2014/11/01 23:44:11]

Scale, rotate and translate are just convenience wrappers around setting an
affine transform (which in turn maps to SkMatrix).
Let's just have an affine transform display item, and put the convenience
wrapper API methods on the AffineTransformRecorder.

[trchen, 2014/11/02 10:36:46]

That makes sense. I was thinking that 2D translation is one important degenerate
case that worth optimizing. (We can implement it without having to save
context.) But I guess we can still use a TransformRecorder to do the recording,
and optimize if we detected the transform was a 2D translation.

+{
+    context->translate(m_translation.width(), m_translation.height());
+}
+
+TranslationRecorder::TranslationRecorder(RenderObject* renderer, GraphicsContext* context, const FloatSize& translation)
+    : m_renderer(renderer)
+    , m_context(context)
+    , m_translation(translation)
+{
+    if (m_translation.isZero())
+        return;
+
+    if (RuntimeEnabledFeatures::slimmingPaintEnabled())
+        ViewDisplayList::fromRenderObject(m_renderer).add(adoptPtr(new TranslationDisplayItem(m_translation)));
+    else
+        context->translate(m_translation.width(), m_translation.height());
+}
+
+TranslationRecorder::~TranslationRecorder()
+{
+    if (m_translation.isZero())
+        return;
+
+    if (RuntimeEnabledFeatures::slimmingPaintEnabled())
+        ViewDisplayList::fromRenderObject(m_renderer).add(adoptPtr(new EndTranslationDisplayItem(m_translation)));
+    else
+        m_context->translate(-m_translation.width(), -m_translation.height());
+}
+
+} // namespace blink