Implement main blink target in GN.

public/blink_devtools.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 12 matching lines @@
 # SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 # 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.
 #
 {
     'targets': [
         {
+            # GN version: //third_party/WebKit/public:blink_devtools_frontend_resources
             'target_name': 'blink_devtools_frontend_resources',
             'type': 'none',
             'dependencies': [
                 '../Source/devtools/devtools.gyp:devtools_frontend_resources',
             ],
         },
         {
+            # GN version: //third_party/WebKit/public:blink_generate_devtools_grd
             'target_name': 'blink_generate_devtools_grd',
             'type': 'none',
             'dependencies': [
                 '../Source/devtools/devtools.gyp:generate_devtools_grd',
             ],
         },
     ],
 }