Before this change: We requests /diff for file1 We processed file1 We requests /diff for file2 ... After this change We prefetch /diff for each file We use pretech of request /diff for file1 We processed file1 ... This is saving at least 100ms per file, for 10 files ~1second. Change-Id: I60c928852f2b7376c724b1c996966ac8f242cc8a