Catch uncaught promise rejections from V8 and log to console.

Source/bindings/core/v8/V8Initializer.cpp

Index: Source/bindings/core/v8/V8Initializer.cpp
diff --git a/Source/bindings/core/v8/V8Initializer.cpp b/Source/bindings/core/v8/V8Initializer.cpp
index f73978540a245000a78a8a178ab3b90a6fb93a5a..3e3157b30eea1a0a7b7052b561545c2c3e07bf16 100644
--- a/Source/bindings/core/v8/V8Initializer.cpp
+++ b/Source/bindings/core/v8/V8Initializer.cpp
@@ -30,6 +30,7 @@
 #include "bindings/core/v8/ScriptCallStackFactory.h"
 #include "bindings/core/v8/ScriptController.h"
 #include "bindings/core/v8/ScriptProfiler.h"
+#include "bindings/core/v8/ScriptValue.h"
 #include "bindings/core/v8/V8Binding.h"
 #include "bindings/core/v8/V8DOMException.h"
 #include "bindings/core/v8/V8ErrorEvent.h"
@@ -45,6 +46,8 @@
 #include "core/frame/LocalDOMWindow.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/csp/ContentSecurityPolicy.h"
+#include "core/inspector/ConsoleMessage.h"
+#include "core/inspector/ScriptArguments.h"
 #include "core/inspector/ScriptCallStack.h"
 #include "platform/EventDispatchForbiddenScope.h"
 #include "platform/TraceEvent.h"
@@ -155,6 +158,78 @@ static void messageHandlerInMainThread(v8::Handle<v8::Message> message, v8::Hand
     }
 }
 
+typedef WillBeHeapDeque<ScriptValue> PromiseRejectMessageQueue;
+
+static PromiseRejectMessageQueue& promiseRejectMessageQueue()
+{
+    DEFINE_STATIC_LOCAL(OwnPtrWillBePersistent<PromiseRejectMessageQueue>, queue, (adoptPtrWillBeNoop(new PromiseRejectMessageQueue())));
+    return *queue;
+}
+
+void V8Initializer::reportRejectedPromises()
+{
+    ASSERT(isMainThread());
+
+    PromiseRejectMessageQueue& queue = promiseRejectMessageQueue();
+    while (!queue.isEmpty()) {
+        ScriptValue promise = queue.takeFirst();
+        ScriptState* scriptState = promise.scriptState();
+        if (!scriptState->contextIsValid())
+            continue;
+        ScriptState::Scope scope(scriptState);
+
+        ASSERT(!promise.isEmpty());
+        v8::Handle<v8::Value> value = promise.v8Value();
+        ASSERT(!value.IsEmpty() && value->IsPromise());
+        if (v8::Handle<v8::Promise>::Cast(value)->HasHandler())
+            continue;
+
+        ExecutionContext* executionContext = scriptState->executionContext();
+        if (!executionContext)
+            continue;
+
+        const String errorMessage = "Unhandled promise rejection";
+        Vector<ScriptValue> args;
+        args.append(ScriptValue(scriptState, v8String(scriptState->isolate(), errorMessage)));
+        args.append(promise);
+        RefPtrWillBeRawPtr<ScriptArguments> arguments = ScriptArguments::create(scriptState, args);
+
+        RefPtrWillBeRawPtr<ConsoleMessage> consoleMessage = ConsoleMessage::create(JSMessageSource, ErrorMessageLevel, errorMessage, "", 0);
+        consoleMessage->setScriptArguments(arguments);
+        executionContext->addConsoleMessage(consoleMessage.release());
+    }
+}
+
+static void promiseRejectHandlerInMainThread(v8::PromiseRejectMessage message)
+{
+    ASSERT(isMainThread());
+
+    if (message.GetEvent() != v8::kPromiseRejectWithNoHandler)
+        return;
+
+    // It's possible that promiseRejectHandlerInMainThread() is invoked while we're initializing a window.
+    // In that half-baked situation, we don't have a valid context nor a valid world,
+    // so just return immediately.
+    if (DOMWrapperWorld::windowIsBeingInitialized())
+        return;
+
+    v8::Handle<v8::Promise> promise = message.GetPromise();
+
+    // Bail out if called during context initialization.
+    v8::Isolate* isolate = promise->GetIsolate();
+    v8::Handle<v8::Context> context = isolate->GetCurrentContext();
+    if (context.IsEmpty())
+        return;
+    v8::Handle<v8::Value> global = V8Window::findInstanceInPrototypeChain(context->Global(), context->GetIsolate());
+    if (global.IsEmpty())
+        return;
+    if (!toFrameIfNotDetached(context))
+        return;
+
+    ScriptState* scriptState = ScriptState::from(context);
+    promiseRejectMessageQueue().append(ScriptValue(scriptState, promise));
+}
+
 static void failedAccessCheckCallbackInMainThread(v8::Local<v8::Object> host, v8::AccessType type, v8::Local<v8::Value> data)
 {
     v8::Isolate* isolate = v8::Isolate::GetCurrent();
@@ -218,6 +293,7 @@ void V8Initializer::initializeMainThreadIfNeeded()
     v8::V8::SetAllowCodeGenerationFromStringsCallback(codeGenerationCheckCallbackInMainThread);
 
     isolate->SetEventLogger(timerTraceProfilerInMainThread);
+    isolate->SetPromiseRejectCallback(promiseRejectHandlerInMainThread);
 
     ScriptProfiler::initialize();
 }