Bug 1331915 Add Telemetry probe to Graphite library usage r=jfkthame

MozReview-Commit-ID: 1aU5ddQoLnV

--HG--
extra : rebase_source : f4237dba387d977f0f6036f7bc5fc15822ea2bf4

gfx/thebes/gfxFont.cpp

@@ -2712,6 +2712,7 @@ gfxFont::ShapeText(DrawTarget      *aDrawTarget,
         if (gfxPlatform::GetPlatform()->UseGraphiteShaping()) {
             if (!mGraphiteShaper) {
                 mGraphiteShaper = MakeUnique<gfxGraphiteShaper>(this);
+                Telemetry::ScalarAdd(Telemetry::ScalarID::BROWSER_USAGE_GRAPHITE, 1);
             }
             ok = mGraphiteShaper->ShapeText(aDrawTarget, aText, aOffset, aLength,
                                             aScript, aVertical, aRounding,

toolkit/components/telemetry/Scalars.yaml

@@ -201,6 +201,21 @@ browser.engagement.navigation:
     record_in_processes:
       - 'main'
 
+# The following section contains the browser usage scalars.
+browser.usage:
+  graphite:
+    bug_numbers:
+      - 1331915
+    description: >
+      The number of times a graphite2 font has been loaded.
+    expires: "60"
+    kind: uint
+    notification_emails:
+      - tom@mozilla.com
+    release_channel_collection: opt-in
+    record_in_processes:
+      -all
+
 # This section is for probes used to measure use of the Webextensions storage.sync API.
 storage.sync.api.usage:
   extensions_using: