BufferQueue/SF: Add OccupancyTracker

Adds an OccupancyTracker to BufferQueue. This module keeps track of
how many buffers are in the queue over time, which, in combination
with various aggregation of these statistics, allows SurfaceFlinger
to report what fraction of the time a given layer was double- or
triple-buffered.

Change-Id: Ida6e967dc5483c00a633e9fe03998e420dd88502
diff --git a/libs/gui/IGraphicBufferConsumer.cpp b/libs/gui/IGraphicBufferConsumer.cpp
index cb1ad35..7c4379f 100644
--- a/libs/gui/IGraphicBufferConsumer.cpp
+++ b/libs/gui/IGraphicBufferConsumer.cpp
@@ -51,6 +51,7 @@
     SET_CONSUMER_USAGE_BITS,
     SET_TRANSFORM_HINT,
     GET_SIDEBAND_STREAM,
+    GET_OCCUPANCY_HISTORY,
     DUMP,
 };
 
@@ -260,6 +261,31 @@
         return stream;
     }
 
+    virtual status_t getOccupancyHistory(bool forceFlush,
+            std::vector<OccupancyTracker::Segment>* outHistory) {
+        Parcel data, reply;
+        data.writeInterfaceToken(IGraphicBufferConsumer::getInterfaceDescriptor());
+        status_t error = data.writeBool(forceFlush);
+        if (error != NO_ERROR) {
+            return error;
+        }
+        error = remote()->transact(GET_OCCUPANCY_HISTORY, data,
+                &reply);
+        if (error != NO_ERROR) {
+            return error;
+        }
+        error = reply.readParcelableVector(outHistory);
+        if (error != NO_ERROR) {
+            return error;
+        }
+        status_t result = NO_ERROR;
+        error = reply.readInt32(&result);
+        if (error != NO_ERROR) {
+            return error;
+        }
+        return result;
+    }
+
     virtual void dump(String8& result, const char* prefix) const {
         Parcel data, reply;
         data.writeInterfaceToken(IGraphicBufferConsumer::getInterfaceDescriptor());
@@ -409,6 +435,25 @@
             }
             return NO_ERROR;
         }
+        case GET_OCCUPANCY_HISTORY: {
+            CHECK_INTERFACE(IGraphicBufferConsumer, data, reply);
+            bool forceFlush = false;
+            status_t error = data.readBool(&forceFlush);
+            if (error != NO_ERROR) {
+                return error;
+            }
+            std::vector<OccupancyTracker::Segment> history;
+            status_t result = getOccupancyHistory(forceFlush, &history);
+            error = reply->writeParcelableVector(history);
+            if (error != NO_ERROR) {
+                return error;
+            }
+            error = reply->writeInt32(result);
+            if (error != NO_ERROR) {
+                return error;
+            }
+            return NO_ERROR;
+        }
         case DUMP: {
             CHECK_INTERFACE(IGraphicBufferConsumer, data, reply);
             String8 result = data.readString8();