Track frame context URL using first script heuristic

third_party/WebKit/Source/core/inspector/InspectorWebPerfAgent.cpp

Index: third_party/WebKit/Source/core/inspector/InspectorWebPerfAgent.cpp
diff --git a/third_party/WebKit/Source/core/inspector/InspectorWebPerfAgent.cpp b/third_party/WebKit/Source/core/inspector/InspectorWebPerfAgent.cpp
index ad4732b0535a11de6d56e0d585d9b953eb97cfea..ca99b2cb9c76934327c9efc4c8e86bee3e3a56b1 100644
--- a/third_party/WebKit/Source/core/inspector/InspectorWebPerfAgent.cpp
+++ b/third_party/WebKit/Source/core/inspector/InspectorWebPerfAgent.cpp
@@ -4,22 +4,40 @@
 
 #include "core/inspector/InspectorWebPerfAgent.h"
 
+#include "core/InstrumentingAgents.h"
 #include "core/frame/LocalFrame.h"
+#include "core/frame/Location.h"
 #include "core/inspector/InspectedFrames.h"
+#include "public/platform/Platform.h"
 
 namespace blink {
 
 InspectorWebPerfAgent::InspectorWebPerfAgent(InspectedFrames* inspectedFrames)
     : m_inspectedFrames(inspectedFrames)
 {
+    Platform::current()->currentThread()->addTaskTimeObserver(this);
+    Platform::current()->currentThread()->addTaskObserver(this);
 }
 
 InspectorWebPerfAgent::~InspectorWebPerfAgent()
 {
+    Platform::current()->currentThread()->removeTaskTimeObserver(this);
+    Platform::current()->currentThread()->removeTaskObserver(this);
 }
 
 void InspectorWebPerfAgent::willExecuteScript(ExecutionContext* context)
 {
+    // Heuristic for minimal frame context attribution: for the first script seen
+    // within a toplevel message loop task - record the URL for the ExecutionContext.
+    if (m_firstScriptSeen)
+        return;
+    m_firstScriptSeen = true;
+    Location* location = context->isDocument() ? toDocument(context)->location() : nullptr;
+    if (location) {
+        m_frameContextURL = std::string(location->protocol().ascii().data()) + "//"
+            + location->hostname().ascii().data()
+            + location->pathname().ascii().data();
+    }
 }
 
 void InspectorWebPerfAgent::didExecuteScript()
@@ -28,6 +46,10 @@ void InspectorWebPerfAgent::didExecuteScript()
 
 void InspectorWebPerfAgent::willProcessTask()
 {
+    // Reset m_frameContextURL. We don't reset this in didProcessTask as
+    // it is needed in ReportTaskTime which occurs after didProcessTask.
+    m_firstScriptSeen = false;
+    m_frameContextURL = "";
 }
 
 void InspectorWebPerfAgent::didProcessTask()