Simplify ContentWatcher by calling querySelector directly instead of through JS.

chrome/renderer/resources/extensions/content_watcher.js

Index: chrome/renderer/resources/extensions/content_watcher.js
diff --git a/chrome/renderer/resources/extensions/content_watcher.js b/chrome/renderer/resources/extensions/content_watcher.js
index 9c118ed9425a8ffc9569420b222972fc65950b21..e34317710613ee7a2bd3c8124591e0247100577f 100644
--- a/chrome/renderer/resources/extensions/content_watcher.js
+++ b/chrome/renderer/resources/extensions/content_watcher.js
@@ -4,21 +4,6 @@
 
 var contentWatcherNative = requireNative("contentWatcherNative");
 
-// Returns the indices in |cssSelectors| that match any element on the page.
-exports.FindMatchingSelectors = function(cssSelectors) {
-  var result = []
-  $Array.forEach(cssSelectors, function(selector, index) {
-    try {
-      if (document.querySelector(selector) != null)
-        $Array.push(result, index);
-    } catch (exception) {
-      throw new Error("query Selector failed on '" + selector + "': " +
-                      exception.stack);
-    }
-  });
-  return result;
-};
-
 // Watches the page for all changes and calls FrameMutated (a C++ callback) in
 // response.
 var mutation_observer = new MutationObserver(contentWatcherNative.FrameMutated);