Avoid too small reads to bufferMoreData()

src/codec/SkRawCodec.cpp

Index: src/codec/SkRawCodec.cpp
diff --git a/src/codec/SkRawCodec.cpp b/src/codec/SkRawCodec.cpp
index da3c28c549ff617cc74df0effb9ff18177eca023..c7de3172863876cdbf1ec0e2d5a2d0111e6ddc3f 100644
--- a/src/codec/SkRawCodec.cpp
+++ b/src/codec/SkRawCodec.cpp
@@ -267,10 +267,13 @@ private:
             return false;
         }
 
-        const size_t sizeToRead = newSize - fStreamBuffer.bytesWritten();
-        SkAutoTMalloc<uint8> tempBuffer(sizeToRead);
+        // Try to read at least 8192 bytes to avoid to many small reads.
+        const size_t kMinSizeToRead = 8192;
+        const size_t sizeRequested = newSize - fStreamBuffer.bytesWritten();
+        const size_t sizeToRead = SkTMax(kMinSizeToRead, sizeRequested);
+        SkAutoSTMalloc<kMinSizeToRead, uint8> tempBuffer(sizeToRead);
         const size_t bytesRead = fStream->read(tempBuffer.get(), sizeToRead);
-        if (bytesRead != sizeToRead) {
+        if (bytesRead < sizeRequested) {
             return false;
         }
         return fStreamBuffer.write(tempBuffer.get(), bytesRead);
@@ -438,9 +441,6 @@ private:
 SkCodec* SkRawCodec::NewFromStream(SkStream* stream) {
     SkAutoTDelete<SkRawStream> rawStream(new SkRawStream(stream));
     ::piex::PreviewImageData imageData;
-    // FIXME: ::piex::GetPreviewImageData() calls GetData() frequently with small amounts,
-    // resulting in many calls to bufferMoreData(). Could we make this more efficient by grouping
-    // smaller requests together?
     if (::piex::IsRaw(rawStream.get())) {
         ::piex::Error error = ::piex::GetPreviewImageData(rawStream.get(), &imageData);