Cleanup warnings configs and enable more for Android ARM64

webrtc/build/common.gypi

Index: webrtc/build/common.gypi
diff --git a/webrtc/build/common.gypi b/webrtc/build/common.gypi
index 304c933c3874d2b2e1acc5df8a1bccaa1cd40bbf..9a79de9eb003e1ad4cd767d56576da54c87c19e6 100644
--- a/webrtc/build/common.gypi
+++ b/webrtc/build/common.gypi
@@ -320,23 +320,13 @@
         ],
         'conditions': [
           ['os_posix==1', {
-            'conditions': [
-              # -Wextra is currently disabled in Chromium's common.gypi. Enable
-              # for targets that can handle it. For Android/arm64 right now
-              # there will be an 'enumeral and non-enumeral type in conditional
-              # expression' warning in android_tools/ndk_experimental's version
-              # of stlport.
-              # See: https://code.google.com/p/chromium/issues/detail?id=379699
-              ['target_arch!="arm64" or OS!="android"', {
-                'cflags': [
-                  '-Wextra',
-                  # We need to repeat some flags from Chromium's common.gypi
-                  # here that get overridden by -Wextra.
-                  '-Wno-unused-parameter',
-                  '-Wno-missing-field-initializers',
-                  '-Wno-strict-overflow',
-                ],
-              }],
+            # Enable more warnings: -Wextra is currently disabled in Chromium.
+            'cflags': [
+              '-Wextra',
+              # Repeat some flags that get overridden by -Wextra.
+              '-Wno-unused-parameter',
+              '-Wno-missing-field-initializers',
+              '-Wno-strict-overflow',
             ],
             'cflags_cc': [
               '-Wnon-virtual-dtor',