Expose HWUI metrics via statsd

Add atom definition for HWUI stats. Implement a C++
statsd puller inside GraphicsStatsService service.
GraphicsStatsService has new private API, which
returns a serialized proto with HWUI stats grouped
by application package and version.

Test: Ran "adb shell cmd stats pull-source 10068"
Test: Ran "statsd_testdrive 10068" and it looks OK
Bug: 142665516
Change-Id: I400c0dbf9e25181d36f9018688b03d86839ac3de
diff --git a/libs/hwui/protos/graphicsstats.proto b/libs/hwui/protos/graphicsstats.proto
index 0cd5c62..dd5676c 100644
--- a/libs/hwui/protos/graphicsstats.proto
+++ b/libs/hwui/protos/graphicsstats.proto
@@ -29,6 +29,11 @@
 }
 
 message GraphicsStatsProto {
+    enum PipelineType {
+        GL = 0;
+        VULKAN = 1;
+    }
+
     // The package name of the app
     optional string package_name = 1;
 
@@ -49,6 +54,9 @@
 
     // The gpu frame time histogram for the package
     repeated GraphicsStatsHistogramBucketProto gpu_histogram = 7;
+
+    // HWUI renders pipeline type: GL or Vulkan
+    optional PipelineType pipeline = 8;
 }
 
 message GraphicsStatsJankSummaryProto {