Bug 1217465 - Fill in missing pixels caused by truncated BMP files. r=seth.

This fixes failures for
image/test/reftest/bmp/bmpsuite/b/{badrle.bmp,shortfile.bmp} with the Skia
back-end.

--HG--
extra : rebase_source : 6c5b967cebf43cf5d49d0e532619bdd1c8ccc69e

image/decoders/nsBMPDecoder.cpp

@@ -240,6 +240,17 @@ nsBMPDecoder::FinishInternal()
   // Send notifications if appropriate.
   if (!IsMetadataDecode() && HasSize()) {
 
+    // If it was truncated, fill in the missing pixels as black.
+    while (mCurrentRow > 0) {
+      uint32_t* dst = RowBuffer();
+      while (mCurrentPos < mH.mWidth) {
+        SetPixel(dst, 0, 0, 0);
+        mCurrentPos++;
+      }
+      mCurrentPos = 0;
+      FinishRow();
+    }
+
     // Invalidate.
     nsIntRect r(0, 0, mH.mWidth, AbsoluteHeight());
     PostInvalidation(r);

image/decoders/nsBMPDecoder.h

@@ -230,8 +230,9 @@ private:
 
   int32_t mCurrentRow;      // Index of the row of the image that's currently
                             // being decoded: [height,1].
-  int32_t mCurrentPos;      // Index into the current line; only used when
-                            // doing RLE decoding.
+  int32_t mCurrentPos;      // Index into the current line. Used when
+                            // doing RLE decoding and when filling in pixels
+                            // for truncated files.
 
   // Only used in RLE_ABSOLUTE state: the number of pixels to read.
   uint32_t mAbsoluteModeNumPixels;