Fix Android compiler warnings.

Review URL: https://codereview.appspot.com/7040053

git-svn-id: http://skia.googlecode.com/svn/trunk@7014 2bbb7eff-a529-9590-31e7-b0007b416f81

include/gpu/GrBackendEffectFactory.h

@@ -63,6 +63,7 @@ protected:
     GrBackendEffectFactory() {
         fEffectClassID = kIllegalEffectClassID;
     }
+    virtual ~GrBackendEffectFactory() {}
 
     static EffectKey GenID() {
         GR_DEBUGCODE(static const int32_t kClassIDBits = 8 * sizeof(EffectKey) -

src/core/SkScan_Antihair.cpp

@@ -89,6 +89,7 @@ static void call_hline_blitter(SkBlitter* blitter, int x, int y, int count,
 class SkAntiHairBlitter {
 public:
     SkAntiHairBlitter() : fBlitter(NULL) {}
+    virtual ~SkAntiHairBlitter() {}
 
     SkBlitter* getBlitter() const { return fBlitter; }