Use .empty() instead of checking .size() == 0 when converting from .isEmpty().

cc/CCLayerTreeHostImpl.cpp

Index: cc/CCLayerTreeHostImpl.cpp
diff --git a/cc/CCLayerTreeHostImpl.cpp b/cc/CCLayerTreeHostImpl.cpp
index 858d9c938dc2b49f80ca199b87c48cdf233d5a09..6892149447f4fcc9d7b9e49e64fef879d175205a 100644
--- a/cc/CCLayerTreeHostImpl.cpp
+++ b/cc/CCLayerTreeHostImpl.cpp
@@ -264,7 +264,7 @@ void CCLayerTreeHostImpl::FrameData::appendRenderPass(scoped_ptr<CCRenderPass> r
 
 bool CCLayerTreeHostImpl::calculateRenderPasses(FrameData& frame)
 {
-    ASSERT(!frame.renderPasses.size());
+    ASSERT(frame.renderPasses.empty());
 
     calculateRenderSurfaceLayerList(*frame.renderSurfaceLayerList);
 
@@ -556,7 +556,7 @@ void CCLayerTreeHostImpl::drawLayers(const FrameData& frame)
 {
     TRACE_EVENT0("cc", "CCLayerTreeHostImpl::drawLayers");
     ASSERT(canDraw());
-    ASSERT(frame.renderPasses.size());
+    ASSERT(!frame.renderPasses.empty());
 
     // FIXME: use the frame begin time from the overall compositor scheduler.
     // This value is currently inaccessible because it is up in Chromium's