Focus SkScaledCodec on BitmapRegionDecoder

The primary goal of SkScaledCodec is to replace the current
implementation of BitmapRegionDecoder, which depends on modified
versions of libjpeg and libpng, with an implementation that uses
standard versions of the libaries. Since BitmapRegionDecoder only
supports PNG, WEBP and JPEG, limit SkScaledCodec to those classes.
We will focus on those three until we complete this primary goal.
Then we can continue to make SkScaledCodec work for other formats.

Fix some bugs in SkScaledCodec::NewFromStream:
- Handle a NULL input stream properly
- Ensure that the input stream is deleted as expected on bad data

Add tests for these error cases.

BUG=skia:4428

Review URL: https://codereview.chromium.org/1389053002

1 files changed, 14 insertions, 11 deletions

diff --git a/src/codec/SkScaledCodec.cpp b/src/codec/SkScaledCodec.cpp
index 65fd93c8c0..fc51613f31 100644
--- a/src/codec/SkScaledCodec.cpp
+++ b/src/codec/SkScaledCodec.cpp
@@ -12,22 +12,25 @@
 
 
 SkCodec* SkScaledCodec::NewFromStream(SkStream* stream) {
-    bool isWebp = SkWebpCodec::IsWebp(stream);
-    if (!stream->rewind()) {
-        return nullptr;
-    }
-    if (isWebp) {
-        // Webp codec supports scaling and subsetting natively
-        return SkWebpCodec::NewFromStream(stream);  
-    }
-
     SkAutoTDelete<SkCodec> codec(SkCodec::NewFromStream(stream));
     if (nullptr == codec) {
         return nullptr;
     }
 
-    // wrap in new SkScaledCodec
-    return new SkScaledCodec(codec.detach());
+    switch (codec->getEncodedFormat()) {
+        case kWEBP_SkEncodedFormat:
+            // Webp codec supports scaling and subsetting natively
+            return codec.detach();
+        case kPNG_SkEncodedFormat:
+        case kJPEG_SkEncodedFormat:
+            // wrap in new SkScaledCodec
+            return new SkScaledCodec(codec.detach());
+        default:
+            // FIXME: SkScaledCodec is temporarily disabled for other formats
+            // while focusing on the formats that are supported by
+            // BitmapRegionDecoder.
+            return nullptr;
+    }
 }
 
 SkCodec* SkScaledCodec::NewFromData(SkData* data) {