Add 'variants' support on Linux for COVERAGE=, PROFILE= and SYMBOLS=.

build/common.gypi

 # Copyright (c) 2009 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'variables': {
     # .gyp files should set chromium_code to 1 if they build Chromium-specific
     # code, as opposed to external code.  This variable is used to control
     # such things as the set of warnings to enable, and whether warnings are
     # treated as errors.
@@ skipping 205 matching lines @@
               '-O0',
               '-g',
             ],
           },
           'Release': {
             'cflags': [
               '-O2',
             ],
           },
         },
+        'variants': {
+          'coverage': {
+            'cflags': ['-fprofile-arcs', '-ftest-coverage'],
+            'ldflags': ['-fprofile-arcs'],
+          },
+          'profile': {
+            'cflags': ['-pg', '-g'],
+            'ldflags': ['-pg'],
+          },
+          'symbols': {
+            'cflags': ['-g'],
+          },
+        },
       },
     }],
     ['OS=="mac"', {
       'target_defaults': {
         'mac_bundle': 0,
         'xcode_settings': {
           'ALWAYS_SEARCH_USER_PATHS': 'NO',
           'GCC_C_LANGUAGE_STANDARD': 'c99',
           'GCC_CW_ASM_SYNTAX': 'NO',
           'GCC_DYNAMIC_NO_PIC': 'YES',
@@ skipping 133 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }