Harden degenerate gradient context handling

Certain inputs produce degenerate values at context creation time only.

Detect such cases after context creation, and abort drawing by returning
a null shader context instead.

BUG=skia:5821
R=reed@google.com,brianosman@google.com
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2397473003

Review-Url: https://codereview.chromium.org/2397473003

1 files changed, 5 insertions, 4 deletions

diff --git a/include/core/SkMatrix.h b/include/core/SkMatrix.h
index 19103843bf..f565a537ba 100644
--- a/include/core/SkMatrix.h
+++ b/include/core/SkMatrix.h
@@ -736,6 +736,11 @@ public:
         this->setTypeMask(mask | kRectStaysRect_Mask);
     }
     
+    /**
+     *  Are all elements of the matrix finite?
+     */
+    bool isFinite() const { return SkScalarsAreFinite(fMat, 9); }
+
 private:
     enum {
         /** Set if the matrix will map a rectangle to another rectangle. This
@@ -768,10 +773,6 @@ private:
     SkScalar         fMat[9];
     mutable uint32_t fTypeMask;
 
-    /** Are all elements of the matrix finite?
-     */
-    bool isFinite() const { return SkScalarsAreFinite(fMat, 9); }
-
     static void ComputeInv(SkScalar dst[9], const SkScalar src[9], double invDet, bool isPersp);
 
     uint8_t computeTypeMask() const;