binder: add getDriverName()

Ass ProcessState::getDriverName() to retrieve the /dev node that
libbinder is initialized with in this process.  This can be used
elsewhere to add debug code that is enabled for only one binder domain
or another.

Test: sailfish

Change-Id: I3ea9f0dcc97204508791bdeb70f790980be278a5
Signed-off-by: Iliyan Malchev <malchev@google.com>
diff --git a/include/binder/ProcessState.h b/include/binder/ProcessState.h
index 05e9d09..1ef045d 100644
--- a/include/binder/ProcessState.h
+++ b/include/binder/ProcessState.h
@@ -69,6 +69,8 @@
             status_t            setThreadPoolMaxThreadCount(size_t maxThreads);
             void                giveThreadPoolName();
 
+            String8             getDriverName();
+
 private:
     friend class IPCThreadState;
     
@@ -86,6 +88,7 @@
 
             handle_entry*       lookupHandleLocked(int32_t handle);
 
+            String8             mDriverName;
             int                 mDriverFD;
             void*               mVMStart;