compositor-worker: Remove code from cc_blink

third_party/WebKit/Source/platform/graphics/CompositorMutableStateProvider.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/CompositorMutableStateProvider.h"
+
+#include "cc/layers/layer_impl.h"
+#include "cc/trees/layer_tree_impl.h"
+#include "platform/graphics/CompositorMutableState.h"
+#include "platform/graphics/CompositorMutation.h"
+#include "wtf/PassOwnPtr.h"
+
+namespace blink {
+
+CompositorMutableStateProvider::CompositorMutableStateProvider(cc::LayerTreeImpl* state, CompositorMutations* mutations)
+    : m_state(state)
+    , m_mutations(mutations)
+{
+}
+
+CompositorMutableStateProvider::~CompositorMutableStateProvider() {}
+
+PassOwnPtr<CompositorMutableState>
+CompositorMutableStateProvider::getMutableStateFor(uint64_t element_id)
+{
+    cc::LayerTreeImpl::ElementLayers layers = m_state->GetMutableLayers(element_id);
+
+    if (!layers.main && !layers.scroll)
+        return nullptr;
+
+    // Ensure that we have an entry in the map for |element_id| but do as few
+    // allocations and queries as possible. This will update the map only if we
+    // have not added a value for |element_id|.
+    auto result = m_mutations->map.add(element_id, nullptr);
+
+    // Only if this is a new entry do we want to allocate a new mutation.
+    if (result.isNewEntry)
+        result.storedValue->value = adoptPtr(new CompositorMutation);
+
+    return adoptPtr(new CompositorMutableState(result.storedValue->value.get(), layers.main, layers.scroll));
+}
+
+} // namespace blink