Removed -Wno-overloaded-virtual warning suppression.

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index e4433e6b5de692ca551bac596e69b44d3170cd4f..adf556336ea2609951fb34043f568cb97cad82f3 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -3087,6 +3087,13 @@
         'variables': { 'clang_warning_flags': ['-Wexit-time-destructors']},
       }],
       ['chromium_code==0', {
+        'variables': {
+          'clang_warning_flags': [
+            # TODO(mgiuca): Move this suppression into individual third-party
+            # libraries as required. http://crbug.com/505301.
+            '-Wno-overloaded-virtual',
+          ],
+        },
         'conditions': [
           [ 'os_posix==1 and OS!="mac" and OS!="ios"', {
             # We don't want to get warnings from third-party code,
@@ -5707,7 +5714,6 @@
                   '-Wno-microsoft',  # http://crbug.com/505296
                   '-Wno-missing-braces',  # http://crbug.com/505297
                   '-Wno-msvc-include',  # http://crbug.com/505299
-                  '-Wno-overloaded-virtual',  # http://crbug.com/505301
                   '-Wno-pointer-sign',  # http://crbug.com/505303
                   '-Wno-reorder',  # http://crbug.com/505304
                   '-Wno-switch',  # http://crbug.com/505308