Remove never-happen if statement in WebExternalTextureLayerImpl.

content/renderer/compositor_bindings/web_external_texture_layer_impl.cc

Index: content/renderer/compositor_bindings/web_external_texture_layer_impl.cc
diff --git a/content/renderer/compositor_bindings/web_external_texture_layer_impl.cc b/content/renderer/compositor_bindings/web_external_texture_layer_impl.cc
index 21d7c5d44746d6b41159f66c1c5a1e63ff32c6cc..a759e5c52345c91f4272e39ae3fe24f43e4b42a4 100644
--- a/content/renderer/compositor_bindings/web_external_texture_layer_impl.cc
+++ b/content/renderer/compositor_bindings/web_external_texture_layer_impl.cc
@@ -113,11 +113,7 @@ void WebExternalTextureLayerImpl::DidReleaseMailbox(
     WebExternalBitmapImpl* bitmap,
     unsigned sync_point,
     bool lost_resource) {
-  if (!layer) {
-    delete bitmap;
-    return;
-  }
-
+  DCHECK(layer);
   blink::WebExternalTextureMailbox available_mailbox;
   memcpy(available_mailbox.name, mailbox.name, sizeof(available_mailbox.name));
   available_mailbox.syncPoint = sync_point;