Add isBuffer to SurfaceFrame

Add a boolean that tells if the SurfaceFrame is representing a buffer or
not. This makes it easy to debug lost/stuck frames in the pending
classification list. Also add a miniDump for SurfaceFrame to enable
debugging the lost frame.

Bug: 182214639
Test: Build and flash
Change-Id: I6ceef46887a021c2f36e76f37fab8368802465a4
diff --git a/services/surfaceflinger/BufferStateLayer.cpp b/services/surfaceflinger/BufferStateLayer.cpp
index e017cdc..e25f1c7 100644
--- a/services/surfaceflinger/BufferStateLayer.cpp
+++ b/services/surfaceflinger/BufferStateLayer.cpp
@@ -177,6 +177,8 @@
         // leak.
         ALOGW("Removing the front of pending jank deque from layer - %s to prevent memory leak",
               mName.c_str());
+        std::string miniDump = mPendingJankClassifications.front()->miniDump();
+        ALOGD("Head SurfaceFrame mini dump\n%s", miniDump.c_str());
         mPendingJankClassifications.pop_front();
     }
     mPendingJankClassifications.emplace_back(surfaceFrame);