Add support for PNG representation in gfx::Image

tools/valgrind/memcheck/suppressions_mac.txt

 # There are three kinds of suppressions in this file:
 # 1. Third party stuff we have no control over.
 #
 # 2. Intentional unit test errors, stuff that is somehow a false positive
 # in our own code, or stuff that is so trivial it's not worth fixing.
 #
 # 3. Suppressions for real chromium bugs that are not yet fixed.
 # These should all be in chromium's bug tracking system.
 # Periodically we should sweep this file and the bug tracker clean by
 # running overnight and removing outdated bugs/suppressions.
@@ skipping 298 matching lines @@
    fun:+[QTCaptureVDIGDevice devicesWithIOType:]
    fun:+[QTCaptureDevice devicesWithIOType:]
    fun:+[QTCaptureDevice inputDevices]
    fun:+[QTCaptureDevice inputDevicesWithMediaType:]
    fun:+[VideoCaptureDeviceQTKit deviceNames]
    fun:_ZN5media18VideoCaptureDevice14GetDeviceNamesEPSt4listINS0_4NameESaIS2_EE
    fun:_ZN5media21VideoCaptureDeviceMac4InitEv
    fun:_ZN5media18VideoCaptureDevice6CreateERKNS0_4NameE
    fun:_ZN5media45VideoCaptureDeviceTest_OpenInvalidDevice_Test8TestBodyEv
 }
+{
+  # See http://crbug.com/141293
+  bug_141293
+  Memcheck:Uninitialized
+  fun:deflateEnd
+  fun:deflateSetDictionary
+  fun:deflate
+  fun:png_write_finish_row
+  fun:png_write_find_filter
+  fun:_cg_png_write_row
+  fun:writeOnePng
+  fun:_CGImagePluginWritePNG
+  fun:CGImageDestinationFinalize
+  fun:+[NSBitmapImageRep(NSBitmapImageFileTypeExtensions) representationOfImageRepsInArray:usingType:properties:]
+  fun:-[NSBitmapImageRep(NSBitmapImageFileTypeExtensions) representationUsingType:properties:]
+  fun:_ZN3gfx8internal14PNGFromNSImageEP7NSImagePSt6vectorIhSaIhEE
+  fun:_ZNK3gfx5Image10ToImagePNGEv
+  fun:_ZN12_GLOBAL__N_143ImageTest_PlatformToPNGEncodeAndDecode_Test8TestBodyEv
+}
 
 # 2. Intentional unit test errors, stuff that is somehow a false positive
 # in our own code, or stuff that is so trivial it's not worth fixing.
 {
    # Plugins are deliberately not unloaded (on shutdown) on the Mac, in order to
    # prevent crashes for those that don't unload cleanly.
    plugin_unload
    Memcheck:Leak
    fun:_Znw*
    fun:_ZN4base17LoadNativeLibraryERK8FilePathPSs
@@ skipping 2104 matching lines @@
    fun:_ZL19ConvertYUVToRGB32_ChhhPh
    fun:LinearScaleYUVToRGB32RowWithRange_C
    fun:_ZN5media23ScaleYUVToRGB32WithRectEPKhS1_S1_Phiiiiiiiiiii
    fun:_ZN8remoting29ConvertAndScaleYUVToRGB32RectEPKhS1_S1_iiRK7SkTSizeIiERK7SkIRectPhiS5_S8_S8_
    fun:_ZN8remoting10DecoderVp811RenderFrameERK7SkTSizeIiERK7SkIRectPhiP8SkRegion
    fun:_ZN8remoting13DecoderTester11RenderFrameEv
    fun:_ZN8remoting13DecoderTester14ReceivedPacketEPNS_11VideoPacketE
    fun:_ZN8remoting13DecoderTester20ReceivedScopedPacketE10scoped_ptrINS_11VideoPacketEE
 }