Fixes for SkPictureShader.

src/core/SkPictureShader.cpp

Index: src/core/SkPictureShader.cpp
diff --git a/src/core/SkPictureShader.cpp b/src/core/SkPictureShader.cpp
index 1e9507190c60a4ac4e8b16785c9dc06948f13e55..76aa857e229297b04d1fa36e5382e701cb791423 100644
--- a/src/core/SkPictureShader.cpp
+++ b/src/core/SkPictureShader.cpp
@@ -19,11 +19,9 @@
 #endif
 
 SkPictureShader::SkPictureShader(SkPicture* picture, TileMode tmx, TileMode tmy)
-    : fPicture(picture)
+    : fPicture(SkRef(picture))
     , fTmx(tmx)
-    , fTmy(tmy) {
-    SkSafeRef(fPicture);
-}
+    , fTmy(tmy) { }
 
 SkPictureShader::SkPictureShader(SkReadBuffer& buffer)
         : INHERITED(buffer) {
@@ -32,15 +30,22 @@ SkPictureShader::SkPictureShader(SkReadBuffer& buffer)
     if (buffer.readBool()) {
         fPicture = SkPicture::CreateFromBuffer(buffer);
     } else {
-        fPicture = NULL;
+        // For backwards compatibility, create a dummy picture. Older versions allowed

[scroggo, 2014/04/15 19:15:49]

This code is only for handling already existing SKPs. If chromium is not yet
using this class, this code can be removed.

[f(malita), 2014/04/15 19:40:40]

Yes, should be safe to remove.

[scroggo, 2014/04/15 20:33:20]

Done.

+        // creating an SkPictureShader with a NULL SkPicture.
+        SkPictureRecorder factory;
+        factory.beginRecording(0, 0);
+        fPicture = factory.endRecording();
     }
 }
 
 SkPictureShader::~SkPictureShader() {
-    SkSafeUnref(fPicture);
+    fPicture->unref();
 }
 
 SkPictureShader* SkPictureShader::Create(SkPicture* picture, TileMode tmx, TileMode tmy) {
+    if (!picture || 0 == picture->width() || 0 == picture->height()) {
+        return NULL;
+    }
     return SkNEW_ARGS(SkPictureShader, (picture, tmx, tmy));
 }
 
@@ -56,9 +61,13 @@ void SkPictureShader::flatten(SkWriteBuffer& buffer) const {
 }
 
 SkShader* SkPictureShader::buildBitmapShader(const SkMatrix& matrix) const {
-    if (!fPicture || (0 == fPicture->width() && 0 == fPicture->height())) {
-        return NULL;
-    }
+    // FIXME: Older versions of this class allowed a picture with 0 width or
+    // height, but would bail out here. Allow a 0 width/height to support
+    // reading an SkPictureShader from an SKP. Note that we will still return
+    // NULL in that case due to an empty tileSize. If/when we can disregard
+    // old SKPs, it is safe to assert the picture's width and height are
+    // greater than zero.

[f(malita), 2014/04/15 19:40:40]

It's safe to disregard old SKPs - the shader is not used at this point.

[scroggo, 2014/04/15 20:33:20]

Done.

+    SkASSERT(fPicture); // && fPicture->width() > 0 && fPicture->height() > 0);
 
     SkMatrix m;
     if (this->hasLocalMatrix()) {