Update libwebp and resume testing scaled webp

DEPS

Index: DEPS
diff --git a/DEPS b/DEPS
index 4439cb08091ca7c92dd1f8925ebe87994030fd69..e316d7d1512558bebaea16f4803e26a6def967cd 100644
--- a/DEPS
+++ b/DEPS
@@ -14,7 +14,8 @@ deps = {
   "third_party/externals/harfbuzz": "https://skia.googlesource.com/third_party/harfbuzz.git@0.9.35",
   "third_party/externals/jsoncpp" : "https://chromium.googlesource.com/external/jsoncpp/jsoncpp.git@1afff032c83e26ddf7f2776e8b43de5ad666c1fa",
   "third_party/externals/libjpeg" : "https://chromium.googlesource.com/chromium/deps/libjpeg_turbo.git@034e9a9747e0983bc19808ea70e469bc8342081f",
-  "third_party/externals/libwebp" : "https://chromium.googlesource.com/webm/libwebp.git@v0.4.3",
+  # Slightly ahead of v 0.4.3, to include the fix for skbug.com/4038
+  "third_party/externals/libwebp" : "https://chromium.googlesource.com/webm/libwebp.git@7df93893dcb73dc45733ab4518ce5ca322c25680",

[scroggo_chromium, 2015/08/07 16:14:10]

Derek, I know we usually like to track specific releases rather than revisions,
but I wanted to get the fix for the uninitialized memory problems so we could
test scaling webp images.

   "third_party/externals/nanomsg" : "https://skia.googlesource.com/third_party/nanomsg.git@0.4-beta",
   "third_party/externals/zlib"    : "https://chromium.googlesource.com/chromium/src/third_party/zlib@4ba7cdd0e7bf49d671645264f839838fc56e1492",
   # NOTE: If we update libpng, we may need to update the generated file at third_party/libpng/pnglibconf.h