Linux: use sandbox binary alongside chrome.

This removes linux_sandbox_path and instead expects sandbox binary
to be in the same directory as chrome (or CHROME_DEVEL_SANDBOX to be
set).

This will be helpful for SxS support on Linux, where the sandbox path
would be different depending on channel.

BUG=38598
R=avi@chromium.org, jln@chromium.org

Review URL: https://codereview.chromium.org/20197003

git-svn-id: http://src.chromium.org/svn/trunk/src/build@215101 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

common.gypi

@@ -949,11 +949,6 @@
     # remaining.
     'win_third_party_warn_as_error%': 'true',
 
-    # This is the location of the sandbox binary. Chrome looks for this before
-    # running the zygote process. If found, and SUID, it will be used to
-    # sandbox the zygote process and, thus, all renderer processes.
-    'linux_sandbox_path%': '',
-
     # Clang stuff.
     'clang%': '<(clang)',
     'make_clang_dir%': 'third_party/llvm-build/Release+Asserts',