Make Android gyp flags more like Linux gyp flags. Fix cases of -Wconversion-null.

tools/gyp/configurations_android.gypi

 # Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 # Definitions for building standalone Dart binaries to run on Android.
 # This is mostly excerpted from:
 # http://src.chromium.org/viewvc/chrome/trunk/src/build/common.gypi
 
 {
   'variables': {
     'android_ndk_root': '<(PRODUCT_DIR)/../../third_party/android_tools/ndk',
   },  # variables
   'target_defaults': {
     'configurations': {
       # It is very important to get the order of the linker arguments correct.
       # Therefore, we put them all in the architecture specific configurations,
       # even though there are many flags in common, to avoid splitting them
       # between two configurations and possibly accidentally mixing up the
       # order.
       'Dart_Android_Base': {
         'abstract': 1,
-        'cflags': [ '-Wno-abi', '-Wall', '-W', '-Wno-unused-parameter',
-                    '-Wnon-virtual-dtor', '-fno-rtti', '-fno-exceptions',],
+        'cflags': [
+          # No -Werror due to warnings in stl.
+          '<@(common_gcc_warning_flags)',
+          '-Wnon-virtual-dtor',
+          '-Wvla',
+          '-Woverloaded-virtual',
+          '-g3',
+          '-ggdb3',
+          '-fno-rtti',
+          '-fno-exceptions',
+        ],
         'target_conditions': [
           ['_toolset=="target"', {
             'defines': [
               'ANDROID',
               'USE_STLPORT=1',
               '__GNU_SOURCE=1',
               '_STLP_USE_PTR_SPECIALIZATIONS=1',
               'HAVE_OFF64_T',
               'HAVE_SYS_UIO_H',
             ],
@@ skipping 271 matching lines @@
             ],
           }],
           ['_toolset=="host"', {
             'ldflags': [ '-pthread' ],
           }],
         ],
       },  # Dart_Android_arm64_Base
     },  # configurations
   },  # target_defaults
 }