Implement HitTestAggregator

components/viz/common/BUILD.gn

Index: components/viz/common/BUILD.gn
diff --git a/components/viz/common/BUILD.gn b/components/viz/common/BUILD.gn
index c9051b67aeb2b33b3690ac99e37c71e312e30a70..73b91ac438313b953ac3d2708c3b4987199fba0b 100644
--- a/components/viz/common/BUILD.gn
+++ b/components/viz/common/BUILD.gn
@@ -6,6 +6,7 @@ import("//testing/test.gni")
 
 source_set("common") {
   sources = [
+    "aggregated_hit_test_region.h",

[danakj, 2017/07/13 15:39:38]

Can you put this in common/hit_test?

We're trying to avoid situations where there is code in a directory that isn't a
leaf in the directory tree.

[gklassen, 2017/07/13 19:59:13]

It was originally in common/hit_test, but I am happy to move it back assuming
this has been agreed by others. 

Done. 

     "frame_sink_id.cc",
     "frame_sink_id.h",
     "frame_sink_id_allocator.h",
@@ -42,6 +43,7 @@ source_set("common") {
     "//mojo/public/cpp/bindings",
     "//skia",
     "//ui/gfx:color_space",
+    "//ui/gfx:geometry_skia",
     "//ui/gfx/geometry",
   ]