Add a basic version of Worklet#import.

third_party/WebKit/Source/modules/worklet/Worklet.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "modules/worklet/Worklet.h"
 
+#include "bindings/core/v8/ScriptPromiseResolver.h"
+#include "bindings/core/v8/ScriptSourceCode.h"
 #include "bindings/core/v8/V8Binding.h"
+#include "bindings/core/v8/WorkerOrWorkletScriptController.h"
+#include "core/dom/DOMException.h"
+#include "core/dom/ExceptionCode.h"
 
 namespace blink {
 
 // static
 Worklet* Worklet::create(ExecutionContext* executionContext)
 {
-    return new Worklet(executionContext);
+    Worklet* worklet = new Worklet(executionContext);
+    worklet->suspendIfNeeded();
+    return worklet;
 }
 
 Worklet::Worklet(ExecutionContext* executionContext)
-    : m_workletGlobalScope(WorkletGlobalScope::create(executionContext->url(), executionContext->userAgent(), toIsolate(executionContext)))
+    : ActiveDOMObject(executionContext)
+    , m_workletGlobalScope(WorkletGlobalScope::create(executionContext->url(), executionContext->userAgent(), executionContext->securityOrigin(), toIsolate(executionContext)))
 {
 }
 
+ScriptPromise Worklet::import(ScriptState* scriptState, const String& url)
+{
+    KURL scriptURL = executionContext()->completeURL(url);
+    if (!scriptURL.isValid()) {
+        return ScriptPromise::rejectWithDOMException(scriptState, DOMException::create(SyntaxError, "'" + url + "' is not a valid URL."));
+    }
+
+    // TODO(ikilpatrick): Perform upfront CSP checks once we decide on a
+    // CSP-policy for worklets.
+
+    ScriptPromiseResolver* resolver = ScriptPromiseResolver::create(scriptState);
+    m_resolvers.append(resolver);
+
+    ScriptPromise promise = resolver->promise();
+
+    // TODO(ikilpatrick): WorkerScriptLoader will need to be extended to allow
+    // module loading support. For now just fetch a 'classic' script.
+    m_scriptLoaders.append(WorkerScriptLoader::create());
+    m_scriptLoaders.last()->loadAsynchronously(*executionContext(), scriptURL, DenyCrossOriginRequests,
+        bind(&Worklet::onResponse, this),
+        bind(&Worklet::onFinished, this, m_scriptLoaders.last().get(), resolver));

[kinuko, 2016/02/12 07:25:44]

In some error cases onFinished could run before returning promise.  Looks like
it's ok but might be good to note that in a comment.

[ikilpatrick, 2016/02/12 22:59:57]

Done.

+
+    return promise;
+}
+
+void Worklet::onResponse()
+{
+    // TODO(ikilpatrick): Add devtools instrumentation on worklet script
+    // resource loading.
+}
+
+void Worklet::onFinished(WorkerScriptLoader* scriptLoader, ScriptPromiseResolver* resolver)
+{
+    if (scriptLoader->failed()) {
+        resolver->reject(DOMException::create(NetworkError));
+    } else {
+        m_workletGlobalScope->script()->evaluate(ScriptSourceCode(scriptLoader->script(), scriptLoader->url()));

[kinuko, 2016/02/12 07:25:45]

Should we catch error event here?

[ikilpatrick, 2016/02/12 22:59:57]

Added note for the current thinking at the moment. Basically if a script has a
SyntaxError - reject, otherwise resolve (even if a script error was thrown).

The reason for this is that a script may have successfully registered classes in
the worklet (which could be used) even if a script throws.

To support this behaviour will need to change WorkerOrWorkletScriptController a
little to support passing back an error code. So will do it in a follow up.

+        resolver->resolve();

[kinuko, 2016/02/12 07:25:45]

Maybe check resolver->executionContext() ||
resolver->executionContext()->activeDOMObjectsAreStopped() before rejecting or
resolving if we want to extend this object's lifetime longer than the parent
document. (Please see my comments around ActiveDOMObject too)

[ikilpatrick, 2016/02/12 22:59:57]

Added guard for the moment.

+    }
+
+    size_t index = m_scriptLoaders.find(scriptLoader);
+
+    ASSERT(index != kNotFound);
+    ASSERT(m_resolvers[index] == resolver);
+
+    m_scriptLoaders.remove(index);
+    m_resolvers.remove(index);
+}
+
+void Worklet::stop()
+{
+    m_workletGlobalScope->script()->willScheduleExecutionTermination();
+
+    for (auto scriptLoader : m_scriptLoaders) {
+        scriptLoader->cancel();
+    }
+}
+
+bool Worklet::hasPendingActivity() const
+{
+    return !m_scriptLoaders.isEmpty();
+}
+
 DEFINE_TRACE(Worklet)
 {
+    visitor->trace(m_resolvers);
     visitor->trace(m_workletGlobalScope);
+    ActiveDOMObject::trace(visitor);
 }
 
 } // namespace blink