Create PaintChunk and begin writing code to build paint chunks.

third_party/WebKit/Source/platform/graphics/paint/PaintChunker.cpp

Index: third_party/WebKit/Source/platform/graphics/paint/PaintChunker.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/paint/PaintChunker.cpp b/third_party/WebKit/Source/platform/graphics/paint/PaintChunker.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..2616ccaef8dbd931ed3f7f535544cd743ad9600c
--- /dev/null
+++ b/third_party/WebKit/Source/platform/graphics/paint/PaintChunker.cpp
@@ -0,0 +1,67 @@
+// Copyright 2015 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 "platform/graphics/paint/PaintChunker.h"
+
+#include "platform/RuntimeEnabledFeatures.h"
+
+namespace blink {
+
+PaintChunker::PaintChunker()
+{
+}
+
+PaintChunker::~PaintChunker()
+{
+}
+
+void PaintChunker::updateCurrentPaintProperties(const PaintProperties& properties)
+{
+    ASSERT(RuntimeEnabledFeatures::slimmingPaintV2Enabled());
+
+    m_currentProperties = properties;
+}
+
+void PaintChunker::incrementDisplayItemIndex()
+{
+    ASSERT(RuntimeEnabledFeatures::slimmingPaintV2Enabled());
+
+    if (m_chunks.isEmpty()) {
+        PaintChunk newChunk(0, 1, m_currentProperties);
+        m_chunks.append(newChunk);
+        return;
+    }
+
+    auto& lastChunk = m_chunks.last();
+    if (m_currentProperties == lastChunk.properties) {
+        lastChunk.endIndex++;
+        return;
+    }
+
+    PaintChunk newChunk(lastChunk.endIndex, lastChunk.endIndex + 1, m_currentProperties);
+    m_chunks.append(newChunk);
+}
+
+void PaintChunker::decrementDisplayItemIndex()
+{
+    ASSERT(RuntimeEnabledFeatures::slimmingPaintV2Enabled());
+    ASSERT(!m_chunks.isEmpty());
+
+    auto& lastChunk = m_chunks.last();
+    if ((lastChunk.endIndex - lastChunk.beginIndex) > 1)
+        lastChunk.endIndex--;
+    else
+        m_chunks.removeLast();
+}
+
+Vector<PaintChunk> PaintChunker::releasePaintChunks()
+{
+    Vector<PaintChunk> chunks;
+    chunks.swap(m_chunks);
+    m_currentProperties = PaintProperties();
+    return chunks;
+}
+
+} // namespace blink