Fix FrameMetricsObserver crash

Bug: 30587465

Someday maybe the technology will exist to
allow sharing a simple constant between
Java and C++, but today is not that day.

Change-Id: I17694746cb8712058133cd5ea10c47b9909f740b

core/java/android/view/FrameMetrics.java

@@ -198,7 +198,7 @@ public final class FrameMetrics {
         int SWAP_BUFFERS = 12;
         int FRAME_COMPLETED = 13;
 
-        int FRAME_STATS_COUNT = 14; // must always be last
+        int FRAME_STATS_COUNT = 16; // must always be last
     }
 
     /*

libs/hwui/FrameInfo.cpp

@@ -43,6 +43,9 @@ static_assert((sizeof(FrameInfoNames)/sizeof(FrameInfoNames[0]))
         == static_cast<int>(FrameInfoIndex::NumIndexes),
         "size mismatch: FrameInfoNames doesn't match the enum!");
 
+static_assert(static_cast<int>(FrameInfoIndex::NumIndexes) == 16,
+        "Must update value in FrameMetrics.java#FRAME_STATS_COUNT (and here)");
+
 void FrameInfo::importUiThreadInfo(int64_t* info) {
     memcpy(mFrameInfo, info, UI_THREAD_FRAME_INFO_SIZE * sizeof(int64_t));
 }

libs/hwui/FrameInfo.h

@@ -52,6 +52,7 @@ enum class FrameInfoIndex {
     QueueBufferDuration,
 
     // Must be the last value!
+    // Also must be kept in sync with FrameMetrics.java#FRAME_STATS_COUNT
     NumIndexes
 };