Revert of add SkMatrix::decomposeScale

src/core/SkBitmapProcState.cpp

Index: src/core/SkBitmapProcState.cpp
diff --git a/src/core/SkBitmapProcState.cpp b/src/core/SkBitmapProcState.cpp
index 0b50fbc32dc8f4d160a78bc54e4b46de300ff14b..720a30f05c4a72b77365237c929755e0c1a4cf17 100644
--- a/src/core/SkBitmapProcState.cpp
+++ b/src/core/SkBitmapProcState.cpp
@@ -98,6 +98,12 @@
     return (dimension & ~0x3FFF) == 0;
 }
 
+static SkScalar effective_matrix_scale(const SkMatrix& mat) {
+    SkScalar dx = SkVector::Length(mat.getScaleX(), mat.getSkewY());
+    SkScalar dy = SkVector::Length(mat.getSkewX(), mat.getScaleY());
+    return SkScalarSqrt(dx * dy);
+}
+
 // Check to see that the size of the bitmap that would be produced by
 // scaling by the given inverted matrix is less than the maximum allowed.
 static inline bool cache_size_okay(const SkBitmap& bm, const SkMatrix& invMat) {
@@ -113,6 +119,22 @@
 }
 
 /*
+ *  Extract the "best" scale factors from a matrix.
+ */
+static bool extract_scale(const SkMatrix& matrix, SkVector* scale) {
+    SkASSERT(!matrix.hasPerspective());
+    SkScalar sx = SkPoint::Length(matrix[SkMatrix::kMScaleX], matrix[SkMatrix::kMSkewY]);
+    SkScalar sy = SkPoint::Length(matrix[SkMatrix::kMSkewX],  matrix[SkMatrix::kMScaleY]);
+    if (!SkScalarIsFinite(sx) || !SkScalarIsFinite(sy) ||
+        SkScalarNearlyZero(sx) || SkScalarNearlyZero(sy))
+    {
+        return false;
+    }
+    scale->set(sx, sy);
+    return true;
+}
+
+/*
  *  High quality is implemented by performing up-right scale-only filtering and then
  *  using bilerp for any remaining transformations.
  */
@@ -132,12 +154,12 @@
     SkScalar invScaleX = fInvMatrix.getScaleX();
     SkScalar invScaleY = fInvMatrix.getScaleY();
     if (fInvMatrix.getType() & SkMatrix::kAffine_Mask) {
-        SkSize scale;
-        if (!fInvMatrix.decomposeScale(&scale)) {
-            return;
-        }
-        invScaleX = scale.width();
-        invScaleY = scale.height();
+        SkVector scale;
+        if (!extract_scale(fInvMatrix, &scale)) {
+            return; // can't find suitable scale factors
+        }
+        invScaleX = scale.x();
+        invScaleY = scale.y();
     }
     if (SkScalarNearlyEqual(invScaleX, 1) && SkScalarNearlyEqual(invScaleY, 1)) {
         return; // no need for HQ
@@ -182,11 +204,7 @@
     // to a valid bitmap.
     fFilterLevel = kLow_SkFilterQuality;
 
-    SkSize invScaleSize;
-    if (!fInvMatrix.decomposeScale(&invScaleSize, NULL)) {
-        return;
-    }
-    SkScalar invScale = SkScalarSqrt(invScaleSize.width() * invScaleSize.height());
+    SkScalar invScale = effective_matrix_scale(fInvMatrix);
 
     if (invScale > SK_Scalar1) {
         fCurrMip.reset(SkMipMapCache::FindAndRef(fOrigBitmap));