[Mac] address perf regressions on bots...

base/mac_util.mm

 // Copyright (c) 2008-2009 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.
 
 #include "base/mac_util.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/file_path.h"
 #include "base/logging.h"
@@ skipping 222 matching lines @@
     // Separate this component from the next one.
     bundle_name += '/';
   }
 
   return FilePath();
 }
 
 bool SetFileBackupExclusion(const FilePath& file_path, bool exclude) {
   NSString* filePath =
       [NSString stringWithUTF8String:file_path.value().c_str()];
+
+  // If being asked to exclude something in a temp directory, just lie and say
+  // it was done.  TimeMachine will already ignore temp directories.  This keeps
+  // the temporary profiles used by unittests from being added to the exclude
+  // list.  Otherwise, as the list grows the bots slow down due to
+  // reading/writes all the temporary profiles used over time.
+  if ([filePath hasPrefix:@"/tmp/"] ||
+      [filePath hasPrefix:@"/var/tmp/"] ||
+      [filePath hasPrefix:@"/private/tmp/"] ||
+      [filePath hasPrefix:@"/private/var/tmp/"]) {
+    return true;
+  }
+
   NSURL* url = [NSURL fileURLWithPath:filePath];
   // Note that we always set CSBackupSetItemExcluded's excludeByPath param
   // to true.  This prevents a problem with toggling the setting: if the file
   // is excluded with excludeByPath set to true then excludeByPath must
   // also be true when un-excluding the file, otherwise the un-excluding
   // will be ignored.
   bool success =
       CSBackupSetItemExcluded((CFURLRef)url, exclude, true) == noErr;
   if (!success)
     LOG(WARNING) << "Failed to set backup excluson for file '"
@@ skipping 20 matching lines @@
                  << " but it was "
                  << base::SysCFStringRefToUTF8(actual_type_ref)
                  << " instead";
     return NULL;
   }
 
   return value;
 }
 
 }  // namespace mac_util