Worklet: Make "unsafe-eval" CSP directive available for worklets

"unsafe-eval" CSP directive is enabled in
WorkerOrWorkletScriptController::Evaluate(). This function is called for classic
script evaluation, not for module script evaluation that worklets depend on.
This means the current implementation doesn't work for worklets.

To enable the directive for worklets, this CL moves the part from Evaluate() to
InitializeContextIfNeeded() that is supposed to be called for both classic and
module script evaluation.

This CL also fixes ExecutionContext handling in
CodeGenerationCheckCallbackInMainThread(). This path is called not only from
Document but also from PaintWorklet.

This change is tested for workers by existing CSP tests, and will be tested for
worklets by tests to be added by a following change:
https://chromium-review.googlesource.com/c/chromium/src/+/771051

Bug: 773786
Change-Id: I29232a4297b2f4819f1fe28f3230fc7ea4f769f6
Reviewed-on: https://chromium-review.googlesource.com/799654Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Hiroki Nakagawa <nhiroki@chromium.org>
Cr-Commit-Position: refs/heads/master@{#520806}

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

@@ -353,8 +353,10 @@ static bool CodeGenerationCheckCallbackInMainThread(
     v8::Local<v8::Context> context,
     v8::Local<v8::String> source) {
   if (ExecutionContext* execution_context = ToExecutionContext(context)) {
+    DCHECK(execution_context->IsDocument() ||
+           execution_context->IsPaintWorkletGlobalScope());
     if (ContentSecurityPolicy* policy =
-            ToDocument(execution_context)->GetContentSecurityPolicy()) {
+            execution_context->GetContentSecurityPolicy()) {
       v8::String::Value source_str(source);
       UChar snippet[ContentSecurityPolicy::kMaxSampleLength + 1];
       size_t len = std::min((sizeof(snippet) / sizeof(UChar)) - 1,

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

@@ -242,6 +242,13 @@ bool WorkerOrWorkletScriptController::InitializeContextIfNeeded(
       context, *world_, global_object, v8::Local<v8::Object>(),
       v8::Local<v8::Function>(), global_interface_template);
 
+  if (!disable_eval_pending_.IsEmpty()) {
+    script_state_->GetContext()->AllowCodeGenerationFromStrings(false);
+    script_state_->GetContext()->SetErrorMessageForCodeGenerationFromStrings(
+        V8String(isolate_, disable_eval_pending_));
+    disable_eval_pending_ = String();
+  }
+
   return true;
 }
 
@@ -260,13 +267,6 @@ ScriptValue WorkerOrWorkletScriptController::Evaluate(
 
   ScriptState::Scope scope(script_state_.get());
 
-  if (!disable_eval_pending_.IsEmpty()) {
-    script_state_->GetContext()->AllowCodeGenerationFromStrings(false);
-    script_state_->GetContext()->SetErrorMessageForCodeGenerationFromStrings(
-        V8String(isolate_, disable_eval_pending_));
-    disable_eval_pending_ = String();
-  }
-
   v8::TryCatch block(isolate_);
 
   v8::Local<v8::Script> compiled_script;