Compress sources of JS libraries in addition to the snapshot.

tools/gyp/v8.gyp

 # Copyright 2011 the V8 project authors. 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
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 12 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': {
     'use_system_v8%': 0,
     'msvs_use_common_release': 0,
     'gcc_version%': 'unknown',
-    'v8_compress_startup_data%': 'false',
+    'v8_compress_startup_data%': 'off',
     'v8_target_arch%': '<(target_arch)',
 
     # Setting 'v8_can_use_unaligned_accesses' to 'true' will allow the code
     # generated by V8 to do unaligned memory access, and setting it to 'false'
     # will ensure that the generated code will always do aligned memory
     # accesses. The default value of 'default' will try to determine the correct
     # setting. Note that for Intel architectures (ia32 and x64) unaligned memory
     # access is allowed for all CPUs.
     'v8_can_use_unaligned_accesses%': 'default',
 
@@ skipping 851 matching lines @@
                 '<@(library_files)',
               ],
               'outputs': [
                 '<(SHARED_INTERMEDIATE_DIR)/libraries.cc',
               ],
               'action': [
                 'python',
                 '../../tools/js2c.py',
                 '<@(_outputs)',
                 'CORE',
+                '<(v8_compress_startup_data)',
                 '<@(library_files)'
               ],
             },
             {
               'action_name': 'js2c_experimental',
               'inputs': [
                 '../../tools/js2c.py',
                 '<@(experimental_library_files)',
               ],
               'outputs': [
                 '<(SHARED_INTERMEDIATE_DIR)/experimental-libraries.cc',
               ],
               'action': [
                 'python',
                 '../../tools/js2c.py',
                 '<@(_outputs)',
                 'EXPERIMENTAL',
+                '<(v8_compress_startup_data)',
                 '<@(experimental_library_files)'
               ],
             },
           ],
         },
         {
           'target_name': 'mksnapshot',
           'type': 'executable',
           'toolsets': ['host'],
           'dependencies': [
@@ skipping 54 matching lines @@
           'target_name': 'v8_shell',
           'type': 'none',
           'dependencies': [
             'v8'
           ],
         },
       ],
     }],
   ],
 }