Check and canonicalize CSS selectors before registering PageStateMatchers.

chrome/renderer/extensions/schema_utils_native_handler.cc

+// Copyright 2013 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 "chrome/renderer/extensions/schema_utils_native_handler.h"
+
+#include "chrome/renderer/extensions/chrome_v8_context.h"
+#include "third_party/WebKit/public/platform/WebString.h"
+#include "third_party/WebKit/public/web/WebScriptBindings.h"
+#include "third_party/WebKit/public/web/WebSelector.h"
+
+namespace extensions {
+
+using WebKit::WebString;
+
+SchemaUtilsNativeHandler::SchemaUtilsNativeHandler(ChromeV8Context* context)
+    : ObjectBackedNativeHandler(context) {
+  RouteFunction(
+      "CanonicalizeCompoundSelector",
+      base::Bind(&SchemaUtilsNativeHandler::CanonicalizeCompoundSelector,
+                 base::Unretained(this)));
+}
+
+void SchemaUtilsNativeHandler::CanonicalizeCompoundSelector(
+    const v8::FunctionCallbackInfo<v8::Value>& args) {
+  CHECK_EQ(args.Length(), 1);
+  v8::Local<v8::Value> arg_string;

[Jeffrey Yasskin, 2013/08/29 03:39:39]

There's an implicit HandleScope around native function calls, right?

[not at google - send to devlin, 2013/08/29 15:20:25]

Yep.

+  {
+    v8::TryCatch block;
+    arg_string = args[0]->ToString();
+    if (block.HasCaught()){
+      block.ReThrow();
+      args.GetReturnValue().Set(v8::Undefined());

[not at google - send to devlin, 2013/08/29 15:20:25]

I imagine that setting a return value after throwing an exception is
meaningless.

(also you probably want to early-return from this method here in this case)

[Jeffrey Yasskin, 2013/08/29 21:46:43]

Yeah, must be, since forgetting to return didn't break anything.
Oops.

+    }

[not at google - send to devlin, 2013/08/29 15:20:25]

I would think that you'd rather throw a schema validation error if this isn't a
string, rather than coercing things into a string. I believe that ToString()
calls the ToString method of the object, which is indeed a problem.

TBH you might find it easier to do all type validation within the JS code. This
method would then become much simpler:

CHECK(args.Length() == 1 && args[0]->IsString());
WebString input_selector =
    WebKit::WebScriptBindings::toWebString(args[0].As<v8::String>());
...

[Jeffrey Yasskin, 2013/08/29 21:46:43]

Sure, done. The schema validator seems to check all this anyway.

+  }
+  WebString input_selector =
+      WebKit::WebScriptBindings::toWebString(arg_string.As<v8::String>());
+  WebString output_selector = WebKit::canonicalizeSelector(
+      input_selector, WebKit::WebSelectorTypeCompound);
+  args.GetReturnValue().Set(WebKit::WebScriptBindings::toV8String(
+      output_selector, context()->v8_context()->GetIsolate()));
+}
+
+}  // namespace extensions