Mojo: (Theoretically) implement the read side of platform handle passing.

mojo/system/channel_unittest.cc

Index: mojo/system/channel_unittest.cc
diff --git a/mojo/system/channel_unittest.cc b/mojo/system/channel_unittest.cc
index a96c4d1b906944c5ff8c4e18b3dbe7d7139c7a4d..a392f3513fa60a917b0080037bf686672c9eb695 100644
--- a/mojo/system/channel_unittest.cc
+++ b/mojo/system/channel_unittest.cc
@@ -139,6 +139,11 @@ class MockRawChannelOnInitFails : public RawChannel {
     CHECK(false);
     return IO_FAILED;
   }
+  virtual scoped_ptr<embedder::PlatformHandleVector> GetReadPlatformHandles(
+      size_t, const void*) OVERRIDE {
+    CHECK(false);
+    return scoped_ptr<embedder::PlatformHandleVector>();
+  }
   virtual IOResult WriteNoLock(size_t*, size_t*) OVERRIDE {
     CHECK(false);
     return IO_FAILED;