Make messageHandlerInMainThread support main-thread worklets.

third_party/WebKit/Source/bindings/core/v8/V8Initializer.cpp

Index: third_party/WebKit/Source/bindings/core/v8/V8Initializer.cpp
diff --git a/third_party/WebKit/Source/bindings/core/v8/V8Initializer.cpp b/third_party/WebKit/Source/bindings/core/v8/V8Initializer.cpp
index 2aae5b22c7a59fd33cd33083d1b7ff233abc770f..df1b3a89933295f91cb6c218cabbd1ea869a4a55 100644
--- a/third_party/WebKit/Source/bindings/core/v8/V8Initializer.cpp
+++ b/third_party/WebKit/Source/bindings/core/v8/V8Initializer.cpp
@@ -111,11 +111,11 @@ static PassRefPtr<ScriptCallStack> extractCallStack(v8::Isolate* isolate, v8::Lo
     return callStack.release();
 }
 
-static String extractResourceName(v8::Local<v8::Message> message, const Document* document)
+static String extractResourceName(v8::Local<v8::Message> message, const ExecutionContext* context)
 {
     v8::Local<v8::Value> resourceName = message->GetScriptOrigin().ResourceName();
-    bool shouldUseDocumentURL = document && (resourceName.IsEmpty() || !resourceName->IsString());
-    return shouldUseDocumentURL ? document->url() : toCoreString(resourceName.As<v8::String>());
+    bool shouldUseDocumentURL = context && context->isDocument() && (resourceName.IsEmpty() || !resourceName->IsString());
+    return shouldUseDocumentURL ? context->url() : toCoreString(resourceName.As<v8::String>());
 }
 
 static String extractMessageForConsole(v8::Isolate* isolate, v8::Local<v8::Value> data)
@@ -146,11 +146,17 @@ static ErrorEvent* createErrorEventFromMesssage(ScriptState* scriptState, v8::Lo
 static void messageHandlerInMainThread(v8::Local<v8::Message> message, v8::Local<v8::Value> data)
 {
     ASSERT(isMainThread());
+
     v8::Isolate* isolate = v8::Isolate::GetCurrent();
-    // If called during context initialization, there will be no entered window.
+    ScriptState* scriptState = ScriptState::current(isolate);
+    ExecutionContext* context = scriptState->getExecutionContext();
+
+    // If called during context initialization, there will be no entered context.
     // TODO(haraken): Add a helper method to get an entered window that may be null.
-    LocalDOMWindow* enteredWindow = toLocalDOMWindow(toDOMWindow(isolate->GetEnteredContext()));
-    if (!enteredWindow || !enteredWindow->isCurrentlyDisplayedInFrame())
+    if (!context)
+        return;
+
+    if (context->isDocument() && !toDocument(context)->domWindow()->isCurrentlyDisplayedInFrame())

[ikilpatrick, 2016/04/13 04:21:09]

Is toDocument(context)->domWindow() safe? (non-null? and equivalent to before?)

[haraken, 2016/04/13 04:38:48]

This can change existing behavior because the entered window can be different
from the ScriptState::current()->getExecutionContext()->domWindow()...

Hmm. It looks like that the current code is wrong anyway. It is mixing
ScriptState::current() and enteredWindow, which are different things...

OK. My proposal is:

- Stop using the entered window. Always use ScriptState::current(). (Actually I
don't know why we've been using the entered window.)

- Add the following check:

ScriptState* scriptState = ScriptState::current(isolate);
if (!scriptState->contextIsValid())  // This check is essentially the same as
the isCurrentlyDisplayedInFrame check.
  return scriptState;

...;  // Use scriptState as you like.

[ikilpatrick, 2016/04/13 23:26:53]

Done. Tried to clean up the other ScriptState checks as well. Now sufficiently
scared about this code :).

         return;
 
     int scriptId = 0;
@@ -162,9 +168,7 @@ static void messageHandlerInMainThread(v8::Local<v8::Message> message, v8::Local
     else if (message->IsSharedCrossOrigin())
         accessControlStatus = SharableCrossOrigin;
 
-    ScriptState* scriptState = ScriptState::current(isolate);
-
-    String resourceName = extractResourceName(message, enteredWindow->document());
+    String resourceName = extractResourceName(message, context);
     ErrorEvent* event = createErrorEventFromMesssage(scriptState, message, resourceName);
 
     String messageForConsole = extractMessageForConsole(isolate, data);
@@ -174,9 +178,11 @@ static void messageHandlerInMainThread(v8::Local<v8::Message> message, v8::Local
     // This method might be called while we're creating a new context. In this case, we
     // avoid storing the exception object, as we can't create a wrapper during context creation.
     // FIXME: Can we even get here during initialization now that we bail out when GetEntered returns an empty handle?
-    LocalFrame* frame = enteredWindow->document()->frame();
-    if (frame && frame->script().existingWindowProxy(scriptState->world())) {
-        V8ErrorHandler::storeExceptionOnErrorEventWrapper(scriptState, event, data, scriptState->context()->Global());
+    if (context->isDocument()) {
+        LocalFrame* frame = toDocument(context)->frame();
+        if (frame && frame->script().existingWindowProxy(scriptState->world())) {
+            V8ErrorHandler::storeExceptionOnErrorEventWrapper(scriptState, event, data, scriptState->context()->Global());
+        }
     }
 
     if (scriptState->world().isPrivateScriptIsolatedWorld()) {
@@ -187,9 +193,9 @@ static void messageHandlerInMainThread(v8::Local<v8::Message> message, v8::Local
         // other isolated worlds (which means that the error events won't fire any event listeners
         // in user's scripts).
         EventDispatchForbiddenScope::AllowUserAgentEvents allowUserAgentEvents;
-        enteredWindow->document()->reportException(event, scriptId, callStack, accessControlStatus);
+        context->reportException(event, scriptId, callStack, accessControlStatus);
     } else {
-        enteredWindow->document()->reportException(event, scriptId, callStack, accessControlStatus);
+        context->reportException(event, scriptId, callStack, accessControlStatus);
     }
 }