add some asserts for mipmaps, and cleanup fFilterLevel if mipping failed

src/core/SkBitmapProcState.cpp

Index: src/core/SkBitmapProcState.cpp
diff --git a/src/core/SkBitmapProcState.cpp b/src/core/SkBitmapProcState.cpp
index 8874e7b4452308e62bcb12e964f3e9d9660ce92f..1936f6a23bd384516aeaae8e20145a566912743e 100644
--- a/src/core/SkBitmapProcState.cpp
+++ b/src/core/SkBitmapProcState.cpp
@@ -263,6 +263,7 @@ bool SkBitmapProcState::possiblyScaleImage() {
             if (mip) {
                 fScaledCacheID = SkScaledImageCache::AddAndLockMip(fOrigBitmap,
                                                                    mip);
+                SkASSERT(mip->getRefCnt() > 1);
                 mip->unref();   // the cache took a ref
                 SkASSERT(fScaledCacheID);
             }
@@ -403,6 +404,12 @@ bool SkBitmapProcState::chooseProcs(const SkMatrix& inv, const SkPaint& paint) {
         return false;
     }
 
+    // If we are "still" kMedium_FilterLevel, then the request was not fulfilled by possiblyScale,
+    // so we downgrade to kLow (so the rest of the sniffing code can assume that)
+    if (SkPaint::kMedium_FilterLevel == fFilterLevel) {
+        fFilterLevel = SkPaint::kLow_FilterLevel;
+    }
+
     bool trivialMatrix = (fInvMatrix.getType() & ~SkMatrix::kTranslate_Mask) == 0;
     bool clampClamp = SkShader::kClamp_TileMode == fTileModeX &&
                       SkShader::kClamp_TileMode == fTileModeY;