Revert "Revert "[TimeStats] Add callback for global stats""

This reverts commit de64c56f39b03f4908200d1ed2fdc9561f86fe2a.

Reason for revert: Rolling forward with fix

Test: adb shell cmd stats pull-source 10062
Change-Id: I981b12a1c5e69aad0c0d3a409d8b90b3399401f4
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 1796476..06a9b1f 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -494,6 +494,7 @@
     ALOGI("Boot is finished (%ld ms)", long(ns2ms(duration)) );
 
     mFrameTracer->initialize();
+    mTimeStats->onBootFinished();
 
     // wait patiently for the window manager death
     const String16 name("window");