[Worklets] Add basic debugging to main thread worklets.

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

Index: third_party/WebKit/Source/core/inspector/InspectorInstrumentation.cpp
diff --git a/third_party/WebKit/Source/core/inspector/InspectorInstrumentation.cpp b/third_party/WebKit/Source/core/inspector/InspectorInstrumentation.cpp
index 77d6c371703b9e338536cbcf1707dc1962085519..3ec19ca54f74a75a5a8af881422106f95f0104cf 100644
--- a/third_party/WebKit/Source/core/inspector/InspectorInstrumentation.cpp
+++ b/third_party/WebKit/Source/core/inspector/InspectorInstrumentation.cpp
@@ -42,6 +42,7 @@
 #include "core/inspector/InstrumentingAgents.h"
 #include "core/inspector/WorkerInspectorController.h"
 #include "core/page/Page.h"
+#include "core/workers/MainThreadWorkletGlobalScope.h"
 #include "core/workers/WorkerGlobalScope.h"
 
 namespace blink {
@@ -173,6 +174,13 @@ InstrumentingAgents* instrumentingAgentsForNonDocumentContext(ExecutionContext*
 {
     if (context->isWorkerGlobalScope())
         return instrumentationForWorkerGlobalScope(toWorkerGlobalScope(context));
+
+    if (context->isWorkletGlobalScope()) {

[pfeldman, 2016/03/15 00:34:56]

Is this only used for the scriptImported instrumentation? It is unfortunate that
we get into the ForNonDocument code path for something that runs on the main
thread. Could you change the call site to use owner local frame in the
instrumentation?

[ikilpatrick, 2016/03/17 16:46:44]

This is used for the willExecuteScript instrumentation, I.e.

#1  0x000000000262d601 in
blink::InspectorInstrumentation::instrumentingAgentsFor 
#2  0x0000000003dfa0ae in blink::InspectorInstrumentation::willExecuteScript 
#3  0x0000000003df6896 in blink::V8ScriptRunner::runCompiledScript 
#4  0x0000000003e0fc3a in blink::WorkerOrWorkletScriptController::evaluate 

I don't think it would make sense to change V8ScriptRunner::runCompiledScript.

Thoughts?

+        LocalFrame* frame = toMainThreadWorkletGlobalScope(context)->frame();
+        if (frame)
+            return instrumentingAgentsFor(frame);
+    }
+
     return 0;
 }