add size limit for using glyphcache. above that, draw using paths

src/core/SkPaint.cpp

Index: src/core/SkPaint.cpp
diff --git a/src/core/SkPaint.cpp b/src/core/SkPaint.cpp
index 9b6b88386339d24a41d3c2f2bd5a3db4115c0dc5..811cbeff9ba8adc15dc54f8ebcdf954db2c0ee18 100644
--- a/src/core/SkPaint.cpp
+++ b/src/core/SkPaint.cpp
@@ -425,6 +425,37 @@ SkAnnotation* SkPaint::setAnnotation(SkAnnotation* annotation) {
 
 ///////////////////////////////////////////////////////////////////////////////
 
+static SkScalar mag2(SkScalar x, SkScalar y) {
+    return x * x + y * y;
+}
+
+static bool tooBig(const SkMatrix& m, SkScalar ma2max) {
+    return  mag2(m[SkMatrix::kMScaleX], m[SkMatrix::kMSkewY]) > ma2max
+            ||
+            mag2(m[SkMatrix::kMSkewX], m[SkMatrix::kMScaleY]) > ma2max;
+}
+
+bool SkPaint::TooBigToUseCache(const SkMatrix& ctm, const SkMatrix& textM) {
+    SkASSERT(!ctm.hasPerspective());
+    SkASSERT(!textM.hasPerspective());
+
+    SkMatrix matrix;
+    matrix.setConcat(ctm, textM);
+    return tooBig(matrix, MaxCacheSize2());
+}
+
+bool SkPaint::tooBigToUseCache(const SkMatrix& ctm) const {
+    SkMatrix textM;
+    return TooBigToUseCache(ctm, *this->setTextMatrix(&textM));
+}
+
+bool SkPaint::tooBigToUseCache() const {
+    SkMatrix textM;
+    return tooBig(*this->setTextMatrix(&textM), MaxCacheSize2());
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
 #include "SkGlyphCache.h"
 #include "SkUtils.h"
 
@@ -1072,7 +1103,7 @@ SkScalar SkPaint::measureText(const void* textData, size_t length,
     SkScalar                            scale = 0;
     SkAutoRestorePaintTextSizeAndFrame  restore(this);
 
-    if (this->isLinearText()) {
+    if (this->isLinearText() || this->tooBigToUseCache()) {
         scale = fTextSize / kCanonicalTextSizeForPaths;
         // this gets restored by restore
         ((SkPaint*)this)->setTextSize(SkIntToScalar(kCanonicalTextSizeForPaths));
@@ -1287,7 +1318,7 @@ int SkPaint::getTextWidths(const void* textData, size_t byteLength,
     SkAutoRestorePaintTextSizeAndFrame  restore(this);
     SkScalar                            scale = 0;
 
-    if (this->isLinearText()) {
+    if (this->isLinearText() || this->tooBigToUseCache()) {
         scale = fTextSize / kCanonicalTextSizeForPaths;
         // this gets restored by restore
         ((SkPaint*)this)->setTextSize(SkIntToScalar(kCanonicalTextSizeForPaths));