Add CSSTiming to collect aggregate PLT-level stats about CSS.

third_party/WebKit/Source/core/timing/PerformanceTiming.cpp

Index: third_party/WebKit/Source/core/timing/PerformanceTiming.cpp
diff --git a/third_party/WebKit/Source/core/timing/PerformanceTiming.cpp b/third_party/WebKit/Source/core/timing/PerformanceTiming.cpp
index 49344bec52b08385f2c423d61a666d7c95d399c4..3247c88553067df759e731d812ee8ba58af4c9a2 100644
--- a/third_party/WebKit/Source/core/timing/PerformanceTiming.cpp
+++ b/third_party/WebKit/Source/core/timing/PerformanceTiming.cpp
@@ -32,6 +32,7 @@
 
 #include "bindings/core/v8/ScriptValue.h"
 #include "bindings/core/v8/V8ObjectBuilder.h"
+#include "core/css/CSSTiming.h"
 #include "core/dom/Document.h"
 #include "core/dom/DocumentParserTiming.h"
 #include "core/dom/DocumentTiming.h"
@@ -402,6 +403,16 @@ PerformanceTiming::parseBlockedOnScriptExecutionFromDocumentWriteDuration()
       timing->parserBlockedOnScriptExecutionFromDocumentWriteDuration());
 }
 
+unsigned long long PerformanceTiming::authorStyleSheetParseDurationBeforeFCP()
+    const {
+  const CSSTiming* timing = cssTiming();
+  if (!timing)
+    return 0;
+
+  return static_cast<unsigned long long>(
+      timing->authorStyleSheetParseDurationBeforeFCP());

[Bryan McQuade, 2016/11/04 14:11:30]

re: returning micros here, for the purpose of page load perf tracking, if you
have a value that's below 1ms, is it useful to know its microsecond resolution,
as opposed to just rounding it up to 1ms, or down to 0ms? my sense is that it's
not really interesting at page load performance scale to track anything beyond
millisecond resolution, and i think there's a lot of value to being consistent
with our existing code, so i'm only supportive of doing this if you really think
we're going to learn something interesting here by having greater than
millisecond resolution.

[Charlie Harrison, 2016/11/04 16:05:19]

Let me try to return second resolution.

+}
+
 DocumentLoader* PerformanceTiming::documentLoader() const {
   if (!frame())
     return nullptr;
@@ -431,6 +442,17 @@ const PaintTiming* PerformanceTiming::paintTiming() const {
   return &PaintTiming::from(*document);
 }
 
+const CSSTiming* PerformanceTiming::cssTiming() const {
+  if (!frame())
+    return nullptr;
+
+  Document* document = frame()->document();
+  if (!document)
+    return nullptr;
+
+  return &CSSTiming::from(*document);
+}
+
 const DocumentParserTiming* PerformanceTiming::documentParserTiming() const {
   if (!frame())
     return nullptr;