Fixed version of https://codereview.chromium.org/748793002

Fixed version of https://codereview.chromium.org/748793002

The original CL falsely added the inherited project path to the hashables
of each child target even if the path wasn't unique. Not only was this
undesired behavior and essentially a bug, but it also created an issue for
very large projects like bling. The time it took to generate the project files
went up from ~2min to over 20min.
See https://code.google.com/p/chromium/issues/detail?id=447801 for more info.

This CL fixes this behavior.

Relanding in git repo.
Original review:
https://codereview.chromium.org/851103007

BUG=447801
R=mark@chromium.org, jsartisohn@google.com

Committed: https://chromium.googlesource.com/external/gyp/+/002ebe4420a3b1c5731f604426393e845a4ca2f3

[Mark Mentovai, 2015-03-02 19:56:29]

LGTM

[bradn, 2015-03-02 19:57:06]

Committed patchset #1 (id:1) manually as
002ebe4420a3b1c5731f604426393e845a4ca2f3.

[natalie, 2015-03-02 23:21:30]

On 2015/03/02 19:57:06, bradn wrote:
> Committed patchset #1 (id:1) manually as
> 002ebe4420a3b1c5731f604426393e845a4ca2f3.

This commit introduces a syntax error when attempting to run `sudo python
setup.py install` on a Mac:

byte-compiling build/bdist.macosx-10.10-intel/egg/gyp/xcodeproj_file.py to
xcodeproj_file.pyc
  File "build/bdist.macosx-10.10-intel/egg/gyp/xcodeproj_file.py", line 2761
    return True if symroots else return inherit_unique_symroot
                                      ^
SyntaxError: invalid syntax

I've encountered this with Mac OS 10.10.2 and whatever version it is that Travis
CI uses for Obj-C builds.

[Mark Mentovai, 2015-03-02 23:45:40]

Johannes, can you fix this up?

[jsartisohn, 2015-03-03 11:24:53]

On 2015/03/02 23:45:40, Mark Mentovai wrote:
> Johannes, can you fix this up?

Sorry, don't know how this happened, I saw you fixed it already. Thanks.
Is there a way to run something like presubmits for a cl. It's like coding into
the dark sometimes, especially because of all the multiplatform stuff.
Again, I'm super sorry for all the trouble. This CL lay dormant on my machine
for over a month. :|