add perf data files to ignores

docs/getting_started.md

 # Getting Started
 
 How to get and build the libyuv code.
 
 ## Pre-requisites
 
 You'll need to have depot tools installed: https://www.chromium.org/developers/how-tos/install-depot-tools
 Refer to chromium instructions for each platform for other prerequisites.
 
 ## Getting the Code
@@ skipping 36 matching lines @@
         "safesync_url": "",
       },
     ];
     target_os = ["android", "unix"];
 
 Then run:
 
     export GYP_DEFINES="OS=android"
     gclient sync
 
+Caveat: Theres an error with Google Play services updates.  If you get the error "Your version of the Google Play services library is not up to date", run the following:
+    cd chromium/src
+    ./build/android/play_services/update.py download
+    cd ../..
+
 For Windows the gclient sync must be done from an Administrator command prompt.
 
 The sync will generate native build files for your environment using gyp (Windows: Visual Studio, OSX: XCode, Linux: make). This generation can also be forced manually: `gclient runhooks`
 
 To get just the source (not buildable):
     git clone https://chromium.googlesource.com/libyuv/libyuv
 
 
 ## Building the Library and Unittests
 
@@ skipping 339 matching lines @@
     git checkout -b mycl -t origin/master
     git pull
     <edit files>
     git add -u
     git commit -m "my change"
     git cl lint
     git cl try
     git cl upload -r a-reviewer@chomium.org -s
     <once approved..>
     git cl land