Add method to retrieve last timestamp.

Change-Id: I24cf462d627c7d15bca2f21d4747af6484f30ecb
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/github.com/ARM-software/HWCPipe/+/414676
Reviewed-by: Craig Stout <cstout@google.com>
diff --git a/gpu_profiler.h b/gpu_profiler.h
index 228c5f5..02dd781 100644
--- a/gpu_profiler.h
+++ b/gpu_profiler.h
@@ -187,6 +187,9 @@
 
 	// Stops the active profiling session
 	virtual void stop() = 0;
+
+	// Timestamp of the last dump.
+	virtual uint64_t timestamp() const = 0;
 };
 
 }        // namespace hwcpipe
diff --git a/vendor/arm/mali/mali_profiler_magma.h b/vendor/arm/mali/mali_profiler_magma.h
index 0a604e5..7652753 100644
--- a/vendor/arm/mali/mali_profiler_magma.h
+++ b/vendor/arm/mali/mali_profiler_magma.h
@@ -61,6 +61,10 @@
 	virtual void                   run() override;
 	virtual const GpuMeasurements &sample() override;
 	virtual void                   stop() override;
+	virtual uint64_t               timestamp() const override
+	{
+		return timestamp_;
+	}
 
   private:
 	GpuCounterSet enabled_counters_{};