Dont try to draw glyphs with unexpected mask formats

src/gpu/GrFontScaler.cpp

Index: src/gpu/GrFontScaler.cpp
diff --git a/src/gpu/GrFontScaler.cpp b/src/gpu/GrFontScaler.cpp
index 84fd58133c634f4936a5aae256280cfeeb575b2d..a06de4f85aecf7e1ab1b53e74eb1eb27f209559b 100644
--- a/src/gpu/GrFontScaler.cpp
+++ b/src/gpu/GrFontScaler.cpp
@@ -103,7 +103,7 @@ void expand_bits(INT_TYPE* dst,
 }
 
 bool GrFontScaler::getPackedGlyphImage(const SkGlyph& glyph, int width, int height, int dstRB,
-                                       void* dst) {
+                                       GrMaskFormat expectedMaskFormat, void* dst) {
     SkASSERT(glyph.fWidth == width);
     SkASSERT(glyph.fHeight == height);
     const void* src = fStrike->findImage(glyph);
@@ -111,6 +111,18 @@ bool GrFontScaler::getPackedGlyphImage(const SkGlyph& glyph, int width, int heig
         return false;
     }
 
+    // crbug:510931
+    // Retrieving the image from the cache can actually change the mask format.  This case is very
+    // uncommon so for now we just draw a clear box for these glyphs.

[robertphillips, 2015/07/30 14:36:26]

this->getPackedGlyphMaskFormat ?

+    if (getPackedGlyphMaskFormat(glyph) != expectedMaskFormat) {
+        const int bpp = GrMaskFormatBytesPerPixel(expectedMaskFormat);
+        for (int y = 0; y < height; y++) {
+            sk_bzero(dst, width * bpp);
+            dst = (char*)dst + dstRB;
+        }
+        return true;
+    }
+
     int srcRB = glyph.rowBytes();
     // The windows font host sometimes has BW glyphs in a non-BW strike. So it is important here to
     // check the glyph's format, not the strike's format, and to be able to convert to any of the
@@ -118,7 +130,7 @@ bool GrFontScaler::getPackedGlyphImage(const SkGlyph& glyph, int width, int heig
     if (SkMask::kBW_Format == glyph.fMaskFormat) {
         // expand bits to our mask type
         const uint8_t* bits = reinterpret_cast<const uint8_t*>(src);

[robertphillips, 2015/07/30 14:36:26]

what happened to the "this->" ?

-        switch (this->getMaskFormat()) {
+        switch (getMaskFormat()) {
             case kA8_GrMaskFormat:{
                 uint8_t* bytes = reinterpret_cast<uint8_t*>(dst);
                 expand_bits(bytes, bits, width, height, dstRB, srcRB);
@@ -135,9 +147,9 @@ bool GrFontScaler::getPackedGlyphImage(const SkGlyph& glyph, int width, int heig
     } else if (srcRB == dstRB) {
         memcpy(dst, src, dstRB * height);
     } else {

[robertphillips, 2015/07/30 14:36:26]

here too ?

-        const int bbp = GrMaskFormatBytesPerPixel(this->getMaskFormat());
+        const int bpp = GrMaskFormatBytesPerPixel(getMaskFormat());
         for (int y = 0; y < height; y++) {
-            memcpy(dst, src, width * bbp);
+            memcpy(dst, src, width * bpp);
             src = (const char*)src + srcRB;
             dst = (char*)dst + dstRB;
         }
@@ -152,6 +164,7 @@ bool GrFontScaler::getPackedGlyphDFImage(const SkGlyph& glyph, int width, int he
     if (NULL == image) {
         return false;
     }
+
     // now generate the distance field
     SkASSERT(dst);
     SkMask::Format maskFormat = static_cast<SkMask::Format>(glyph.fMaskFormat);