Add renderer launch count to stability metrics.

components/metrics/proto/system_profile.proto

Index: components/metrics/proto/system_profile.proto
diff --git a/components/metrics/proto/system_profile.proto b/components/metrics/proto/system_profile.proto
index d814b3597fe76c2723396e4aa1616f49ab109866..1bf90ef47b09da04d6658f3572a277cfd0e9d676 100644
--- a/components/metrics/proto/system_profile.proto
+++ b/components/metrics/proto/system_profile.proto
@@ -440,7 +440,7 @@ message SystemProfileProto {
   // Figures that can be used to generate application stability metrics.
   // All values are counts of events since the last time that these
   // values were reported.
-  // Next tag: 26
+  // Next tag: 28
   message Stability {
     // Total amount of time that the program was running, in seconds,
     // since the last time a log was recorded, as measured using a client-side
@@ -458,17 +458,19 @@ message SystemProfileProto {
     // This field was added for M-35.
     optional int64 uptime_sec = 23;
 
-    // Page loads along with renderer crashes, hangs and failed launches, since
-    // page load count roughly corresponds to usage.
+    // Page loads along with renderer launches, crashes, hangs and failed
+    // launches, since page load count roughly corresponds to usage.
     optional int32 page_load_count = 2;
     optional int32 renderer_crash_count = 3;
     optional int32 renderer_hang_count = 4;
     optional int32 renderer_failed_launch_count = 24;
+    optional int32 renderer_launch_count = 26;
 
-    // Number of renderer crashes and failed launches that were for extensions.
-    // These are not counted in the renderer counts above.
+    // Number of renderer launches, crashes and failed launches that were for
+    // extensions. These are not counted in the renderer counts above.
     optional int32 extension_renderer_crash_count = 5;
     optional int32 extension_renderer_failed_launch_count = 25;
+    optional int32 extension_renderer_launch_count = 27;
 
     // Number of non-renderer child process crashes.
     optional int32 child_process_crash_count = 6;