Add blink_gc_plugin variable to enable the clang plugin for checking GC consistency.

Source/config.gyp

 #
 # Copyright (C) 2013 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
@@ skipping 14 matching lines @@
 # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #
 {
   'variables': {
     # If set to 1, doesn't compile debug symbols into webcore reducing the
     # size of the binary and increasing the speed of gdb.  gcc only.
     'remove_webcore_debug_symbols%': 0,
+    # Set to 1 to check GC infrastructure when compiling with clang.

[Mads Ager (chromium), 2014/01/10 09:20:50]

Maybe write this out a bit more:

Set to 1 to enable the clang plugin that checks the usage of the Blink
garbage-collection infrastructure during compilation.

?

[zerny-chromium, 2014/01/10 09:53:49]

Done.

+    # Requires building locally since GOMA doesn't yet support the plugin.
+    'blink_gc_plugin%': 0,
   },
   'targets': [
   {
     'target_name': 'config',
     'type': 'none',
     'direct_dependent_settings': {
       'include_dirs': [
         '.',
         '..',
       ],
@@ skipping 46 matching lines @@
           # Due to a bug in gcc arm, we get warnings about uninitialized
           # timesNewRoman.unstatic.3258 and colorTransparent.unstatic.4879.
           'cflags': ['-Wno-uninitialized'],
         }],
         ['clang==1', {
           'cflags': ['-Wglobal-constructors'],
           'xcode_settings': {
             'WARNING_CFLAGS': ['-Wglobal-constructors'],
           },
         }],
+        # Only enable the blink_gc_plugin when using clang.
+        ['clang==1 and blink_gc_plugin==1', {
+          'cflags': ['<!@(../../../tools/clang/scripts/blink_gc_plugin_flags.sh)'],

[Mads Ager (chromium), 2014/01/10 09:20:50]

This is dotting its way far outside of the Blink directory. Since the chromium
and blink repos are currently separate that doesn't seem ideal. Should we move
this flag further out in the gyp structure? We have other clang plugins that are
run over the Blink sources, right? Where are they enabled? Could we move this
enabling there so it is more local?

[zerny-chromium, 2014/01/10 09:53:49]

Not as far as I can see. Currently the active plugin (FindBadConstructs) is
explicitly disabled for WebKit/blink. However, it is run on all files and the
plugin itself ignores any structures in the WebKit/blink namespace.

In our present case, it seem proper to only enable the gc plugin when compiling
blink source files (as done in this CL). Maybe we could read the plugin flags
into a blink_gc_plugin_flags gyp variable and then use that to set cflags inside
blink.

+        }],
       ],
     },
   },
   {
     'target_name': 'unittest_config',
     'type': 'none',
     'dependencies': [
       'config',
       '<(DEPTH)/testing/gmock.gyp:gmock',
       '<(DEPTH)/testing/gtest.gyp:gtest',
     ],
     'export_dependent_settings': [
       'config',
       '<(DEPTH)/testing/gmock.gyp:gmock',
       '<(DEPTH)/testing/gtest.gyp:gtest',
     ],
     'direct_dependent_settings': {
       'cflags!': ['-Wglobal-constructors'],
       'xcode_settings': {
         'WARNING_CFLAGS!': ['-Wglobal-constructors'],
       },
     },
   }
   ],
 }