managing chromes use section of docs

site/dev/chrome/blink.md

+How to land Skia changes that change Blink layout test results
+==============================================================
+
+Changes that affect a small number of layout test results
+---------------------------------------------------------
+Changes affecting fewer than ~20 layout tests can be rebaselined without special
+coordination with the Blink gardener using these steps:
+
+1. Prepare your Skia change, taking note of which layout tests will turn red
+   \(see http://www.chromium.org/developers/testing/webkit-layout-tests for more
+   detail on running the Blink layout tests\).
+2. Check in your code to the Skia repo.
+3. Ahead of the Skia auto roll including your change, manually push a change to the 
+   Blink LayoutTests/TestExpectations [file](http://src.chromium.org/viewvc/blink/trunk/LayoutTests/TestExpectations),
+   flagging tests expected to fail as a result of your change with \[ NeedsManualRebaseline \].
+4. Wait for the Skia roll to land successfully.
+5. Check in another change to the Blink TestExpectations file changing the flags to 
+   \[ NeedsRebaseline\], which will prompt the automatic rebaseline. 
+
+
+
+Changes that affect a large number of test results 
+--------------------------------------------------
+Where a 'large number' or 'many' means more than about 20.  
+Follow the instructions below:
+
+In the following the term 'code suppression' means a build flag \(a\.k\.a\. define\).
+Such code suppressions should be given a name with the form SK\_IGNORE\_xxx\_FIX.
+
+There are dependency revisions which must be updated in this
+process. Updating a dependency revision is called a 'roll'. 
+There are two different rolls which concern this process, each of which happens
+via an Auto Roll Bot multiple times per day, and can also be done manually:
+    
+  * Skia roll into Chromium. See
+https://chromium.googlesource.com/chromium/src/+log/master/DEPS and search for
+skia\-deps\-roller.
+  * Blink roll into Chromium. See
+https://chromium.googlesource.com/chromium/src/+log/master/DEPS and search for
+blink\-deps\-roller.
+
+### Setup
+#### Code suppression does not yet exist \- Direct method 
+1. Make a change in Skia which will change many Blink layout tests.
+2. Put the change behind a code suppression.  
+3. Check in the change to the Skia repository.
+4. Manually roll Skia or append the autoroll with the code suppression to 
+   Chromium's 'skia/skia\_common\.gypi'  
+5. Add code suppression to Blink's 'public/blink\_skia\_config\.gyp'.  
+6. Wait for Blink roll into Chromium.
+7. Remove code suppression from Chromium's 'skia/skia\_common\.gypi'.  
+
+#### Code suppression does not yet exist \- Alternate method
+1. Add code suppression to Blink's 'public/blink\_skia\_config\.gyp' before making code
+   changes in Skia.  
+2. Make a change in Skia which will change many Blink layout tests.
+3. Put the change behind a code suppression.
+4. Wait for Blink roll into Chromium.
+5. Check in the change to the Skia repository.
+6. Wait for Skia roll into Chromium.
+ 
+#### Code suppression exists in header
+1. Remove code suppression from header file in Chromium and add code suppression to
+   Chromium's 'skia/skia\_common\.gypi'.  
+   The code suppression cannot be in a header file and a defined in a gyp file at the 
+   same time or a multiple definition warning will be treated as an error and break 
+   the Chromium build.
+2. Add code suppression to Blink's 'public/blink\_skia\_config\.gyp'.
+3. Wait for Blink roll into Chromium.
+4. Remove code suppression from Chromium's 'skia/skia\_common\.gypi'.
+
+### Rebaseline
+1. Choose a time when the Blink tree is likely to be quiet. Avoid PST afternoons in
+   particular. The bigger the change, the more important this is. Regardless,
+   determine who the Blink gardener is and notify them. You will be making the
+   Chromium\.WebKit tree very red for an extended period, and the gardener needs to
+   know that they are not expected to fix it.  
+2. Create a CL removing the code suppression from Blink's
+   public/blink_skia_config.gyp while simultaneously adding [ NeedsRebaseline ]
+   lines to blink's LayoutTests/TestExpectations [file](http://src.chromium.org/viewvc/blink/trunk/LayoutTests/TestExpectations). 

[bungeman-skia, 2015/02/18 20:42:25]

nit: s/blink/Blink/

+   Then the auto rebaseline bot will take care of the work of actually checking in the 
+   new images. This is generally acceptable for up to 600 or so rebaselined images. 
+   Above that you might still use [ NeedsRebaseline ], but it's best to coordinate with 
+   the gardener/sheriff. This should go through the CQ cleanly. 
+3. Be careful with tests that are already failing or flakey. These may or may not need 
+   to be rebaselined and flakey tests should not be removed from TestExpectations 
+   regardless. In such cases revert the TestExpectations changes before committing.  
+4. If you are not the one handling the cleanup step, please open a Skia Issue of the 
+   form
+   Title: "Remove code suppression SK\_IGNORE\_xxx\_FIX\."
+   Comment: "Code suppression SK\_IGNORE\_xxx\_FIX rebaselined with Blink revision
+   123456\." and assign it to the individual responsible for the cleanup step.
+ 
+### Cleanup
+1. Wait for Blink roll into Chromium, so that Chromium is using the new Skia code
+   and new Blink baselines.  
+2. Remove the now unused old code from Skia and any defines which were introduced 
+   to suppress the new code.
+3. Check in the cleanup change to the Skia repository.
+4. Wait for Skia roll into Chromium.
+