Lazy SKP image decoding in DM.

src/images/SkImageDecoder_libjpeg.cpp

Index: src/images/SkImageDecoder_libjpeg.cpp
diff --git a/src/images/SkImageDecoder_libjpeg.cpp b/src/images/SkImageDecoder_libjpeg.cpp
index d32e2a21c91bea0fe06e472a5e6cce22518f41c5..caa1300124443a5f81aba764ea0d0d4e4d963fe0 100644
--- a/src/images/SkImageDecoder_libjpeg.cpp
+++ b/src/images/SkImageDecoder_libjpeg.cpp
@@ -768,14 +768,25 @@ static SkISize compute_yuv_size(const jpeg_decompress_struct& info, int componen
                          info.cur_comp_info[component]->downsampled_height);
 }
 
-static void update_components_sizes(const jpeg_decompress_struct& cinfo, SkISize componentSizes[3],
+static bool contains_three_planes(const jpeg_decompress_struct& cinfo) {

[hal.canary, 2015/03/17 21:32:48]

// Either explain why this is needed or note that you don't know why it is
needed.

+    return cinfo.cur_comp_info[0] && cinfo.cur_comp_info[1] && cinfo.cur_comp_info[2];
+}
+
+static bool update_components_sizes(const jpeg_decompress_struct& cinfo, SkISize componentSizes[3],
                                     SizeType sizeType) {
+    if (!contains_three_planes(cinfo)) {
+        return false;
+    }
     for (int i = 0; i < 3; ++i) {
         componentSizes[i] = compute_yuv_size(cinfo, i, sizeType);
     }
+    return true;
 }
 
 static bool output_raw_data(jpeg_decompress_struct& cinfo, void* planes[3], size_t rowBytes[3]) {
+    if (!contains_three_planes(cinfo)) {
+        return false;
+    }
     // U size and V size have to be the same if we're calling output_raw_data()
     SkISize uvSize = compute_yuv_size(cinfo, 1, kSizeForMemoryAllocation_SizeType);
     SkASSERT(uvSize == compute_yuv_size(cinfo, 2, kSizeForMemoryAllocation_SizeType));
@@ -897,8 +908,7 @@ bool SkJPEGImageDecoder::onDecodeYUV8Planes(SkStream* stream, SkISize componentS
     cinfo.raw_data_out = TRUE;
 
     if (!planes || !planes[0] || !rowBytes || !rowBytes[0]) { // Compute size only
-        update_components_sizes(cinfo, componentSizes, kSizeForMemoryAllocation_SizeType);
-        return true;
+        return update_components_sizes(cinfo, componentSizes, kSizeForMemoryAllocation_SizeType);
     }
 
     set_dct_method(*this, &cinfo);
@@ -924,7 +934,9 @@ bool SkJPEGImageDecoder::onDecodeYUV8Planes(SkStream* stream, SkISize componentS
         return return_false(cinfo, "output_raw_data");
     }
 
-    update_components_sizes(cinfo, componentSizes, kActualSize_SizeType);
+    if (!update_components_sizes(cinfo, componentSizes, kActualSize_SizeType)) {
+        return false;
+    }
     jpeg_finish_decompress(&cinfo);
 
     if (NULL != colorSpace) {