Revert to enabling all of -O2 as it exposes a bug in the toolchain.

gyp/common_conditions.gypi

 # conditions used in both common.gypi and skia.gyp in chromium
 #
 {
   'defines': [
     'SK_ALLOW_STATIC_GLOBAL_INITIALIZERS=<(skia_static_initializers)',
     'SK_SUPPORT_GPU=<(skia_gpu)',
     'SK_SUPPORT_OPENCL=<(skia_opencl)',
     'SK_FORCE_DISTANCEFIELD_FONTS=<(skia_force_distancefield_fonts)',
     'SK_PICTURE_USE_SK_RECORD',
   ],
@@ skipping 222 matching lines @@
           }],
           # For profiling; reveals some costs, exaggerates others (e.g. trivial setters & getters).
           [ 'skia_disable_inlining', {
             'cflags': [
               '-fno-inline',
               '-fno-default-inline',
               '-finline-limit=0',
               '-fno-omit-frame-pointer',
             ],
           }],
-          [ 'skia_arch_type == "arm64"', {
-            # this flag causes tiling errors with GCC 4.9 (pre-release) toolchain
-            # see skbug.com/ 
-            'cflags': [
-              '-fno-expensive-optimizations'
-            ],
-          }],
           [ 'skia_arch_type == "arm" and arm_thumb == 1', {
             'cflags': [
               '-mthumb',
             ],
             # The --fix-cortex-a8 switch enables a link-time workaround for
             # an erratum in certain Cortex-A8 processors.  The workaround is
             # enabled by default if you target the ARM v7-A arch profile.
             # It can be enabled otherwise by specifying --fix-cortex-a8, or
             # disabled unconditionally by specifying --no-fix-cortex-a8.
             #
@@ skipping 376 matching lines @@
     [ 'skia_is_bot', {
       'defines': [ 'SK_CRASH_HANDLER' ],
     }],
 
   ], # end 'conditions'
   # The Xcode SYMROOT must be at the root. See build/common.gypi in chromium for more details
   'xcode_settings': {
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }