Callback API Change: Allow Bind() to take a Callback<> and bind all its free parameters.

base/bind.h.pump

Index: base/bind.h.pump
diff --git a/base/bind.h.pump b/base/bind.h.pump
index 62b313f666fcaabd4357e6bb1ef59e2d1053b284..eca00cdd0773edf9606a120f0fc431f7f9624887 100644
--- a/base/bind.h.pump
+++ b/base/bind.h.pump
@@ -63,6 +63,26 @@ $for BOUND_ARG , [[P$(BOUND_ARG)]]>(
 }
 
 ]]
+]]  $$ for BOUND
+
+// Specializations to allow binding all the free arguments in a
+// pre-existing base::Callback<>. This does not give full support for
+// currying, but is significantly simpler and addresses the use case
+// where a base::Callback<> needs to be invoked on another context/thread.
+$for BOUND [[
+$range BOUND_ARG 1..BOUND
+$if BOUND != 0 [[
+
+template <typename Sig, $for BOUND_ARG , [[typename P$(BOUND_ARG)]]>
+base::Closure Bind(const base::Callback<Sig>& callback, [[]]
+$for BOUND_ARG , [[const P$(BOUND_ARG)& p$(BOUND_ARG)]]) {
+  return base::Bind([[]]
+&internal::BindMoreFunc$(BOUND)<Sig, $for BOUND_ARG , [[P$(BOUND_ARG)]]>, [[]]
+callback, [[]]
+$for BOUND_ARG , [[p$(BOUND_ARG)]]);
+}
+
+]]
 
 ]]  $$ for BOUND