path ops : make it real

Add an option to SkCanvas to turn on path
ops when combining clips. 

Allow Op() to use one of the input paths
as an output path.

Fix a bug in Op() when the minuend is empty
and the subtrahend is not (for difference).

Change the build to allow core to depend on pathops.
Review URL: https://codereview.chromium.org/14474002

git-svn-id: http://skia.googlecode.com/svn/trunk@8855 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gyp/tests.gyp b/gyp/tests.gyp
index ef6994e..8e82d1b 100644
--- a/gyp/tests.gyp
+++ b/gyp/tests.gyp
@@ -11,13 +11,13 @@
         '../src/core',
         '../src/effects',
         '../src/lazy',
+        '../src/pathops',
         '../src/pdf',
         '../src/pipe/utils',
         '../src/utils',
         '../tools/',
       ],
       'includes': [
-        'pathops.gypi',
         'pathops_unittest.gypi',
       ],
       'sources': [