style plugin: Don't ignore style warnings on the linux clang trybots.

Two parts:
1.) Let the banned_directories_ require full directory matches, not
    just suffixes.
2.) Remove "clang" from banned_directories_. Now that mac builds just
    go into xcodebuild / out, it's no longer required.

Regressed in http://codereview.chromium.org/7824047

BUG=97452
TEST=Try jobs to linux_clang report style problems again.
tools/clang/plugin/tests/test.sh passes again.

Review URL: http://codereview.chromium.org/7980045

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@102344 0039d316-1c4b-4281-b951-d872f2087c98

tools/clang/plugins/ChromeClassTester.cpp

@@ -54,7 +54,6 @@ void ChromeClassTester::BuildBannedLists() {
   banned_directories_.push_back("llvm/");
   banned_directories_.push_back("ninja/");
   banned_directories_.push_back("xcodebuild/");
-  banned_directories_.push_back("clang/");
 
   // You are standing in a mazy of twisty dependencies, all resolved by
   // putting everything in the header.
@@ -233,8 +232,14 @@ bool ChromeClassTester::InBannedDirectory(SourceLocation loc) {
          it != banned_directories_.end(); ++it) {
       // If we can find any of the banned path components in this path, then
       // this file is rejected.
-      if (b.find(*it) != std::string::npos)
-        return true;
+      size_t index = b.find(*it);
+      if (index != std::string::npos) {
+        bool matches_full_dir_name = index == 0 || b[index - 1] == '/';
+        if ((*it)[0] == '/')
+          matches_full_dir_name = true;
+        if (matches_full_dir_name)
+          return true;
+      }
     }
   }