Fix invalid array access in OnRobustJPEGDecodeImage().

This doesn't seem to be a problem for release builds, but in debug builds the invalid array access causes STL errors:

    error: attempt to subscript container with out-of-bounds index 0, but
    container only holds 0 elements.

BUG=401161

Review URL: https://codereview.chromium.org/446853002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@287884 0039d316-1c4b-4281-b951-d872f2087c98

chrome/utility/chrome_content_utility_client.cc

@@ -232,7 +232,8 @@ void ChromeContentUtilityClient::OnCreateZipFile(
 void ChromeContentUtilityClient::OnRobustJPEGDecodeImage(
     const std::vector<unsigned char>& encoded_data) {
   // Our robust jpeg decoding is using IJG libjpeg.
-  if (gfx::JPEGCodec::JpegLibraryVariant() == gfx::JPEGCodec::IJG_LIBJPEG) {
+  if (gfx::JPEGCodec::JpegLibraryVariant() == gfx::JPEGCodec::IJG_LIBJPEG &&
+      !encoded_data.empty()) {
     scoped_ptr<SkBitmap> decoded_image(gfx::JPEGCodec::Decode(
         &encoded_data[0], encoded_data.size()));
     if (!decoded_image.get() || decoded_image->empty()) {