Make lost context callback a base::Closure thru the WGC3DProvider.

third_party/WebKit/public/platform/callback/DEPS

Index: third_party/WebKit/public/platform/callback/DEPS
diff --git a/third_party/WebKit/public/platform/callback/DEPS b/third_party/WebKit/public/platform/callback/DEPS
new file mode 100644
index 0000000000000000000000000000000000000000..a8b824547e30f0930ba871af576b2d93e166d287
--- /dev/null
+++ b/third_party/WebKit/public/platform/callback/DEPS
@@ -0,0 +1,11 @@
+include_rules = [
+    # Bind/Callback is only allowed in rare cases, here it's allowed to convert
+    # from WTF::Function to base::Callback in order to pass callbacks out of
+    # blink.
+    "+base/bind.h",
+    "+base/callback.h",
+    "+base/callback_helpers.h",
+    "+base/logging.h",
+    "+base/macros.h",
+    "+base/memory/scoped_ptr.h",
+]