enable -Wstring-conversion when compiling with clang

Summary of try run with flag enabled as warning:

On linux_clang, there's false positives from a bunch of assert usage that does !"string" or "string" for a true or false value. It's only in third_party (Mesa, skia, libjingle, etc.) so it probably wouldn't be too hard to disable the warnings in those subtrees.

It diagnoses 4 useful locations:

1.
../../base/debug/trace_event_unittest.cc:70:41: warning: implicit conversion turns string literal into bool: 'const char [2]' to 'bool' [-Wstring-conversion]
    TraceLog::GetInstance()->SetEnabled("*");
    ~~~~~~~~                            ^~~

2.
../../sync/syncable/entry_kernel.cc:77:38: warning: implicit conversion turns string literal into bool: 'const char [5]' to 'bool' [-Wstring-conversion]
      value->SetBoolean("encrypted", "true");
      ~~~~~                          ^~~~~~

3.
../../chrome/browser/webdata/web_data_service.cc:334:17: warning: implicit conversion turns string literal into bool: 'const char [44]' to 'bool' [-Wstring-conversion]
    DLOG_ASSERT("WebDataService dtor called without Shutdown");
    ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../base/logging.h:595:43: note: expanded from macro 'DLOG_ASSERT'

4.
../../chrome/browser/renderer_host/web_cache_manager_unittest.cc:259:20: warning: implicit conversion turns string literal into bool: 'const char [29]' to 'bool' [-Wstring-conversion]
      EXPECT_FALSE("Unexpected entry in strategy");
      ~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


Finding #1 is what made me look into this, #3 and #4 are not doing what they're supposed to, and #2 is kind of funny so not all is lost.

So, 3 bugs and 1 very-close-to-a-bug: seems worth enabling.

R=thakis@chromium.org
TBR=darin@chromium.org, dhollowa@chromium.org, brettw@chromium.org, zea@chromium.org
BUG=177306

Review URL: https://chromiumcodereview.appspot.com/12258039

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@183998 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 12 insertions, 0 deletions

diff --git a/skia/skia.gyp b/skia/skia.gyp
index be1a52f..5b32431 100644
--- a/skia/skia.gyp
+++ b/skia/skia.gyp
@@ -540,6 +540,18 @@
             ],
           },
         }],
+        # TODO(scottmg): http://crbug.com/177306
+        ['clang==1', {
+          'xcode_settings': {
+            'WARNING_CFLAGS!': [
+              # Don't warn about string->bool used in asserts.
+              '-Wstring-conversion',
+            ],
+          },
+          'cflags!': [
+            '-Wstring-conversion',
+          ],
+        }],
       ],
       'dependencies': [
         'skia_opts',