For the immediate milestone, exclude History and Thumbnails from being backed...

base/mac_util_unittest.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.
 
 #import <Cocoa/Cocoa.h>
 #include <vector>
 
 #include "base/mac_util.h"
 
 #include "base/file_path.h"
+#include "base/file_util.h"
 #include "base/scoped_nsobject.h"
 #include "base/scoped_ptr.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/platform_test.h"
 
 typedef PlatformTest MacUtilTest;
 
 TEST_F(MacUtilTest, TestFSRef) {
   FSRef ref;
   std::string path("/System/Library");
@@ skipping 73 matching lines @@
     { "/Applications/Google Foo.app/bar/Foo Helper.app/quux/Foo Helper",
         "/Applications/Google Foo.app" },
   };
   for (size_t i = 0; i < ARRAYSIZE_UNSAFE(valid_inputs); i++) {
     out = mac_util::GetAppBundlePath(FilePath(valid_inputs[i].in));
     EXPECT_FALSE(out.empty()) << "loop: " << i;
     EXPECT_STREQ(valid_inputs[i].expected_out,
         out.value().c_str()) << "loop: " << i;
   }
 }
+
+TEST_F(MacUtilTest, TestExcludeFileFromBackups) {
+  NSString* homeDirectory = NSHomeDirectory();
+  NSString* dummyFilePath =
+      [homeDirectory stringByAppendingPathComponent:@"DummyFile"];
+  const char* dummy_file_path = [dummyFilePath fileSystemRepresentation];
+  ASSERT_TRUE(dummy_file_path);
+  FilePath file_path(dummy_file_path);
+  // It is not actually necessary to have a physical file in order to
+  // set its exclusion property.
+  NSURL* fileURL = [NSURL URLWithString:dummyFilePath];
+  // Reset the exclusion in case it was set previously.
+  mac_util::SetFileBackupExclusion(file_path, false);
+  Boolean excludeByPath;
+  // Initial state should be non-excluded.
+  EXPECT_FALSE(CSBackupIsItemExcluded((CFURLRef)fileURL, &excludeByPath));
+  // Exclude the file.
+  EXPECT_TRUE(mac_util::SetFileBackupExclusion(file_path, true));
+  EXPECT_TRUE(CSBackupIsItemExcluded((CFURLRef)fileURL, &excludeByPath));
+  // Un-exclude the file.
+  EXPECT_TRUE(mac_util::SetFileBackupExclusion(file_path, false));
+  EXPECT_FALSE(CSBackupIsItemExcluded((CFURLRef)fileURL, &excludeByPath));
+}