Add gyp define for optimization level

gyp/common_conditions.gypi

Index: gyp/common_conditions.gypi
===================================================================
--- gyp/common_conditions.gypi	(revision 9698)
+++ gyp/common_conditions.gypi	(working copy)
@@ -76,7 +76,7 @@
             'msvs_settings': {
               'VCCLCompilerTool': {
                 'DebugInformationFormat': '3',      # programDatabase (/Zi)
-                'Optimization': '3',                # full (/Ox)
+                'Optimization': '<(skia_release_optimization_level)',
                 'WholeProgramOptimization': 'true', #/GL
                # Changing the floating point model requires rebaseling gm images
                #'FloatingPointModel': '2',          # fast (/fp:fast)
@@ -137,7 +137,10 @@
             'cflags': ['-g']
           },
           'Release': {
-            'cflags': ['-O3 -g'],
+            'cflags': [
+              '-O<(skia_release_optimization_level)',
+              '-g',
+            ],
             'defines': [ 'NDEBUG' ],
           },
         },
@@ -235,7 +238,7 @@
           },
           'Release': {
             'xcode_settings': {
-              'GCC_OPTIMIZATION_LEVEL': '3',
+              'GCC_OPTIMIZATION_LEVEL': '<(skia_release_optimization_level)',
             },
             'defines': [ 'NDEBUG' ],
           },
@@ -301,7 +304,7 @@
           },
           'Release': {
             'xcode_settings': {
-              'GCC_OPTIMIZATION_LEVEL': '3',
+              'GCC_OPTIMIZATION_LEVEL': '<(skia_release_optimization_level)',
             },
             'defines': [ 'NDEBUG' ],
           },