[android] Generate strings.xml for android_webview.

content/content.gyp

Index: content/content.gyp
diff --git a/content/content.gyp b/content/content.gyp
index 5cc87475f728cd4582b5e178936d5736d73d84d6..d2e91f5848494ac45ee3e74a9e05b28144db139a 100644
--- a/content/content.gyp
+++ b/content/content.gyp
@@ -421,6 +421,7 @@
             '../ui/android/ui_android.gyp:ui_java',
             'common_aidl',
             'content_common',
+            'content_strings_grd',
             'gesture_event_type_java',
             'page_transition_types_java',
             'popup_item_type_java',
@@ -447,6 +448,16 @@
           'includes': [ '../build/java.gypi' ],
         },
         {
+          'target_name': 'content_strings_grd',
+          'type': 'none',
+          'variables': {
+            'grd_file': '../content/public/android/java/strings/android_content_strings.grd',
+          },
+          'includes': [
+            '../build/java_strings_grd.gypi',
+          ],
+        },
+        {
           'target_name': 'gesture_event_type_java',
           'type': 'none',
           'sources': [