Verify that contentsTextureManager is non-NULL before dereferencing it.

cc/single_thread_proxy.cc

Index: cc/single_thread_proxy.cc
diff --git a/cc/single_thread_proxy.cc b/cc/single_thread_proxy.cc
index 5cbe3d209ee02c12ca53ca783e982eb4137f8fa5..b4d673aff94e6bc816568d967cbc8a8e038aa4f0 100644
--- a/cc/single_thread_proxy.cc
+++ b/cc/single_thread_proxy.cc
@@ -289,11 +289,17 @@ bool SingleThreadProxy::reduceContentsTextureMemoryOnImplThread(size_t limitByte
 void SingleThreadProxy::sendManagedMemoryStats()
 {
     DCHECK(Proxy::isImplThread());
-    if (m_layerTreeHostImpl.get() && m_layerTreeHostImpl->renderer())
-        m_layerTreeHostImpl->renderer()->sendManagedMemoryStats(
-            m_layerTreeHost->contentsTextureManager()->memoryVisibleBytes(),
-            m_layerTreeHost->contentsTextureManager()->memoryVisibleAndNearbyBytes(),
-            m_layerTreeHost->contentsTextureManager()->memoryUseBytes());
+    if (!m_layerTreeHostImpl.get())
+        return;
+    if (!m_layerTreeHostImpl->renderer())
+        return;
+    if (!m_layerTreeHost->contentsTextureManager())
+        return;
+
+    m_layerTreeHostImpl->renderer()->sendManagedMemoryStats(
+        m_layerTreeHost->contentsTextureManager()->memoryVisibleBytes(),
+        m_layerTreeHost->contentsTextureManager()->memoryVisibleAndNearbyBytes(),
+        m_layerTreeHost->contentsTextureManager()->memoryUseBytes());
 }
 
 // Called by the legacy scheduling path (e.g. where render_widget does the scheduling)