Add skia_clang_build gyp define, add -Wstring-conversion flag

gyp/common_variables.gypi

Index: gyp/common_variables.gypi
===================================================================
--- gyp/common_variables.gypi	(revision 10839)
+++ gyp/common_variables.gypi	(working copy)
@@ -78,6 +78,7 @@
         }],
       ],
 
+      'skia_asan_build%': 0,
       'skia_scalar%': 'float',
       'skia_mesa%': 0,
       'skia_nv_path_rendering%': 0,
@@ -117,6 +118,11 @@
       }, {
         'skia_release_optimization_level%': '<(skia_default_gcc_optimization_level)',
       }],
+      [ 'skia_asan_build', {
+        'skia_clang_build': 1,
+      }, {

[robertphillips, 2013/08/21 14:12:51]

Should this % be here and not above?

[borenet, 2013/08/21 14:16:01]

Building with ASAN implies that we're using Clang, so we force
skia_clang_build=1 in that case.  Otherwise, we use what's provided in
GYP_DEFINES with 0 as the default.

+        'skia_clang_build%': 0,
+      }],
     ],
 
     # Re-define all variables defined within the level-2 'variables' dict,
@@ -126,6 +132,7 @@
     'arm_neon_optional%': 0,
     'skia_os%': '<(skia_os)',
     'os_posix%': '<(os_posix)',
+    'skia_asan_build%': '<(skia_asan_build)',

[djsollen, 2013/08/21 14:09:37]

don't you need to define skia_clang_build here as well?

[borenet, 2013/08/21 14:16:01]

No, since skia_clang_build is already defined at this level.

     'skia_scalar%': '<(skia_scalar)',
     'skia_mesa%': '<(skia_mesa)',
     'skia_nv_path_rendering%': '<(skia_nv_path_rendering)',
@@ -145,7 +152,6 @@
     'skia_static_initializers%': '<(skia_static_initializers)',
     'ios_sdk_version%': '6.0',
     'skia_win_debuggers_path%': '<(skia_win_debuggers_path)',
-    'skia_asan_build%': 0,
 
     # These are referenced by our .gypi files that list files (e.g. core.gypi)
     #