Add a UI for setting JS flags.

The UI only shows up when 'about:debug' is typed in the address bar.
JS flags are a string '--heap-stats --log-gc' in V8 etc.

Currently this is only used by V8 build for debugging purpose.
diff --git a/src/com/android/browser/BrowserActivity.java b/src/com/android/browser/BrowserActivity.java
index 8336837..1c2c6af 100644
--- a/src/com/android/browser/BrowserActivity.java
+++ b/src/com/android/browser/BrowserActivity.java
@@ -783,6 +783,11 @@
             // are not animating from the tab picker.
             attachTabToContentView(mTabControl.getCurrentTab());
         }
+        // Read JavaScript flags if it exists.
+        String jsFlags = mSettings.getJsFlags();
+        if (jsFlags.trim().length() != 0) {
+            mTabControl.getCurrentWebView().setJsFlags(jsFlags);
+        }
 
         /* enables registration for changes in network status from
            http stack */