Make verbose log of graphics layer tree work with the original vmodule string

We use "--vmodule=*/paint/*=3,*/graphics/*=3" to output verbose log
for painting. However it had been mismatching the graphics layer tree
log by renderer/core/frame/local_frame_view.cc after crrev.com/823365.

Move the verbose log for graphics layer trees into
renderer/core/paint/compositing/graphics_layer_tree_as_text.cc to
make the original vmodule string work again.

Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I5ba5147904cf0cb7060a66c7cef8498a4e9fd001
Reviewed-on: https://chromium-review.googlesource.com/1178564
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Reviewed-by: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583918}

third_party/blink/renderer/core/frame/local_frame_view.cc

@@ -2774,17 +2774,7 @@ static void PaintGraphicsLayerRecursively(GraphicsLayer* layer) {
   layer->PaintRecursively();
 
 #if DCHECK_IS_ON()
-  if (VLOG_IS_ON(2)) {
-    DEFINE_STATIC_LOCAL(String, s_previous_tree, ());
-    LayerTreeFlags flags = VLOG_IS_ON(3) ? 0xffffffff : kOutputAsLayerTree;
-    String new_tree = GraphicsLayerTreeAsTextForTesting(layer, flags);
-    if (new_tree != s_previous_tree) {
-      VLOG(2) << "After GraphicsLayer::PaintRecursively()\n"
-              << "GraphicsLayer tree:\n"
-              << new_tree.Utf8().data();
-      s_previous_tree = new_tree;
-    }
-  }
+  VerboseLogGraphicsLayerTree(layer);
 #endif
 }
 

third_party/blink/renderer/core/paint/compositing/graphics_layer_tree_as_text.cc

@@ -352,6 +352,24 @@ String GraphicsLayerTreeAsTextForTesting(const GraphicsLayer* layer,
   return GraphicsLayerTreeAsJSON(layer, flags)->ToPrettyJSONString();
 }
 
+#if DCHECK_IS_ON()
+void VerboseLogGraphicsLayerTree(const GraphicsLayer* root) {
+  if (!VLOG_IS_ON(2))
+    return;
+
+  using GraphicsLayerTreeMap = HashMap<const GraphicsLayer*, String>;
+  DEFINE_STATIC_LOCAL(GraphicsLayerTreeMap, s_previous_trees, ());
+  LayerTreeFlags flags = VLOG_IS_ON(3) ? 0xffffffff : kOutputAsLayerTree;
+  String new_tree = GraphicsLayerTreeAsTextForTesting(root, flags);
+  auto it = s_previous_trees.find(root);
+  if (it == s_previous_trees.end() || it->value != new_tree) {
+    VLOG(2) << "GraphicsLayer tree:\n" << new_tree.Utf8().data();
+    s_previous_trees.Set(root, new_tree);
+    // For simplification, we don't remove deleted GraphicsLayers from the map.
+  }
+}
+#endif
+
 }  // namespace blink
 
 #if DCHECK_IS_ON()

third_party/blink/renderer/core/paint/compositing/graphics_layer_tree_as_text.h

@@ -21,6 +21,9 @@ std::unique_ptr<JSONObject> GraphicsLayerTreeAsJSON(const GraphicsLayer*,
 String CORE_EXPORT GraphicsLayerTreeAsTextForTesting(const GraphicsLayer*,
                                                      LayerTreeFlags);
 
+#if DCHECK_IS_ON()
+void CORE_EXPORT VerboseLogGraphicsLayerTree(const GraphicsLayer*);
+#endif
 }  // namespace blink
 
 #if DCHECK_IS_ON()