Change Deque<RecycledBitmap> to Vector in DrawingBuffer

third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp

Index: third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp b/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp
index a52ced06f4bf74aa35e26669e9f0f9deb85ebb71..7024c53ab22997f1f2a9810e9e17032c97893882 100644
--- a/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp
+++ b/third_party/WebKit/Source/platform/graphics/gpu/DrawingBuffer.cpp
@@ -246,14 +246,16 @@ void DrawingBuffer::freeRecycledMailboxes()
 
 std::unique_ptr<cc::SharedBitmap> DrawingBuffer::createOrRecycleBitmap()
 {
-    for (auto it = m_recycledBitmapQueue.begin(); it != m_recycledBitmapQueue.end(); ++it) {
-        if (it->size != m_size) {
-            m_recycledBitmapQueue.remove(it);
-            --it; // Removed this position so iterate on it again.
-        }
+    size_t i = 0;
+    while (i < m_recycledBitmap.size()) {
+        if (m_recycledBitmap[i].size != m_size)
+            m_recycledBitmap.remove(i); // Removed this position so iterate on it again.

[esprehn, 2016/09/28 23:41:05]

This is causing a bunch of vector resizing and copying. I think you want to
create a new Vector on the stack, copy into it all the values which do match
m_size, and then swap() with the m_recycledBitmap member. That's the more
idiomatic way to do this in blink.

+        else
+            ++i;
     }
-    if (!m_recycledBitmapQueue.isEmpty()) {
-        RecycledBitmap recycled = m_recycledBitmapQueue.takeLast();
+    if (!m_recycledBitmap.isEmpty()) {
+        RecycledBitmap recycled = std::move(m_recycledBitmap.last());
+        m_recycledBitmap.removeLast();

[Ken Russell (switch to Gerrit), 2016/09/20 22:55:37]

Is there any more efficient way of implementing this?

Is it worth adding a takeLast() operation to wtf/Vector.h?

[xidachen, 2016/09/21 14:18:15]

When I looked at Deque::takeLast(), it includes the same steps as here:
T oldLast = std::move(last());
removeLast();
return oldLast;

         DCHECK(recycled.size == m_size);
         return std::move(recycled.bitmap);
     }
@@ -414,7 +416,7 @@ void DrawingBuffer::softwareMailboxReleased(std::unique_ptr<cc::SharedBitmap> bi
         return; // Just delete the bitmap.
 
     RecycledBitmap recycled = { std::move(bitmap), m_size };
-    m_recycledBitmapQueue.append(std::move(recycled));
+    m_recycledBitmap.append(std::move(recycled));
 }
 
 PassRefPtr<StaticBitmapImage> DrawingBuffer::transferToStaticBitmapImage()