Use const reference in setGpuStats() API

Rather than make a copy of these strings when the function is
called, we pass them by const reference.

Test: TreeHugger
Change-Id: Ief53fea1f6df191181e00eab978cf53b5a2ab91d
diff --git a/libs/graphicsenv/IGpuService.cpp b/libs/graphicsenv/IGpuService.cpp
index 98a6395..762a27b 100644
--- a/libs/graphicsenv/IGpuService.cpp
+++ b/libs/graphicsenv/IGpuService.cpp
@@ -27,9 +27,9 @@
 public:
     explicit BpGpuService(const sp<IBinder>& impl) : BpInterface<IGpuService>(impl) {}
 
-    virtual void setGpuStats(const std::string driverPackageName,
-                             const std::string driverVersionName, const uint64_t driverVersionCode,
-                             const std::string appPackageName) {
+    virtual void setGpuStats(const std::string& driverPackageName,
+                             const std::string& driverVersionName, const uint64_t driverVersionCode,
+                             const std::string& appPackageName) {
         Parcel data, reply;
         data.writeInterfaceToken(IGpuService::getInterfaceDescriptor());