ui: Add debug flag to show composited layer borders in ChromeOS UI.

ui/compositor/compositor.cc

Index: ui/compositor/compositor.cc
diff --git a/ui/compositor/compositor.cc b/ui/compositor/compositor.cc
index f69e71ee0dda95a7e88a164c674a9c403348a2b9..4b552a16bd32421d3195876f0ba04e2ee4266dff 100644
--- a/ui/compositor/compositor.cc
+++ b/ui/compositor/compositor.cc
@@ -15,6 +15,7 @@
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/stl_util.h"
+#include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "base/sys_info.h"
 #include "base/trace_event/trace_event.h"
@@ -108,9 +109,26 @@ Compositor::Compositor(const cc::FrameSinkId& frame_sink_id,
   settings.renderer_settings.show_overdraw_feedback =
       command_line->HasSwitch(cc::switches::kShowOverdrawFeedback);
 
-  // These flags should be mirrored by renderer versions in content/renderer/.
-  settings.initial_debug_state.show_debug_borders =
-      command_line->HasSwitch(cc::switches::kUIShowCompositedLayerBorders);
+  if (command_line->HasSwitch(cc::switches::kUIShowCompositedLayerBorders)) {

[danakj, 2017/04/13 15:25:51]

I'd like --ui-show-composited-layer-borders (with no =stuff) to do the same
thing as before, ie empty string means all. This makes the about:flags stuff a
bit simpler and harder to mess up if we add new ones, as we don't have to list
everything in the all case.

[reveman, 2017/04/13 17:00:46]

Done.

+    std::string layer_borders_string = command_line->GetSwitchValueASCII(
+        cc::switches::kUIShowCompositedLayerBorders);
+    std::vector<std::string> entries = base::SplitString(
+        layer_borders_string, ",", base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL);
+    for (const auto& entry : entries) {
+      const struct {
+        const char* name;
+        cc::DebugBorderType type;
+      } kBorders[] = {{"renderpass", cc::DebugBorderType::RENDERPASS},
+                      {"surface", cc::DebugBorderType::SURFACE},
+                      {"layer", cc::DebugBorderType::LAYER}};
+      for (const auto& border : kBorders) {
+        if (border.name == entry) {
+          settings.initial_debug_state.show_debug_borders.set(border.type);
+          break;
+        }
+      }
+    }
+  }
   settings.initial_debug_state.show_fps_counter =
       command_line->HasSwitch(cc::switches::kUIShowFPSCounter);
   settings.initial_debug_state.show_layer_animation_bounds_rects =