Mark layers that can use LCD text based on layer transform and opacity.

cc/content_layer.cc

Index: cc/content_layer.cc
diff --git a/cc/content_layer.cc b/cc/content_layer.cc
index b34ce107e0ced197af3d767f4dc3b8c67f74016f..fcf714bcb8bd15ac935a82b9b409b2f319baa442 100644
--- a/cc/content_layer.cc
+++ b/cc/content_layer.cc
@@ -4,6 +4,7 @@
 
 #include "cc/content_layer.h"
 
+#include "base/debug/trace_event.h"
 #include "base/metrics/histogram.h"
 #include "base/time.h"
 #include "cc/bitmap_content_layer_updater.h"
@@ -14,6 +15,9 @@
 
 namespace cc {
 
+// Maximum number of times LCD text setting can be changed.
+static const int kLCDTextMaxChangeCount = 1;
+
 ContentLayerPainter::ContentLayerPainter(ContentLayerClient* client)
     : m_client(client)
 {
@@ -42,6 +46,7 @@ scoped_refptr<ContentLayer> ContentLayer::create(ContentLayerClient* client)
 ContentLayer::ContentLayer(ContentLayerClient* client)
     : TiledLayer()
     , m_client(client)
+    , m_lcdTextChangeCount(0)
 {
 }
 
@@ -103,4 +108,28 @@ void ContentLayer::setContentsOpaque(bool opaque)
         m_updater->setOpaque(opaque);
 }
 
+bool ContentLayer::canUseLCDTextWillChange()
+{
+    // Always allow disabling LCD text.
+    if (canUseLCDText())
+        return true;
+
+    return m_lcdTextChangeCount < kLCDTextMaxChangeCount;
+}
+
+void ContentLayer::canUseLCDTextDidChange()
+{
+    TiledLayer::canUseLCDTextDidChange();
+
+    if (m_lcdTextChangeCount > 0) {
+        // Do not record the first time LCD text is enabled because
+        // it does not really cause any invalidation.
+        TRACE_EVENT_INSTANT0("cc", "ContentLayer::canUseLCDTextDidChange");
+    }
+    ++m_lcdTextChangeCount;
+
+    // Need to repaint the layer with different text AA setting.
+    setNeedsDisplay();
+}
+
 }  // namespace cc