codec2: Add C2Alloctor::checkHandle()

This patch adds a virtual checkHandle() to simplify some ugly
logic in the vndk/C2Buffer.cpp to determine the subclass and
call that class' isValid() function.

Signed-off-by: John Stultz <john.stultz@linaro.org>
Change-Id: I6447a920f6d889742369f773d8be56ca8a973cae
diff --git a/media/codec2/vndk/internal/C2HandleIonInternal.h b/media/codec2/vndk/internal/C2HandleIonInternal.h
index c0e1d83..c67698c 100644
--- a/media/codec2/vndk/internal/C2HandleIonInternal.h
+++ b/media/codec2/vndk/internal/C2HandleIonInternal.h
@@ -28,7 +28,10 @@
           mFds{ bufferFd },
           mInts{ int(size & 0xFFFFFFFF), int((uint64_t(size) >> 32) & 0xFFFFFFFF), kMagic } { }
 
-    static bool isValid(const C2Handle * const o);
+    static bool IsValid(const C2Handle * const o);
+
+    // deprecated
+    static bool isValid(const C2Handle * const o) { return IsValid(o); }
 
     int bufferFd() const { return mFds.mBuffer; }
     size_t size() const {