Add a DCHECK in mojo/public/cpp/system/handle.h

Bug: 821030
Change-Id: Iec0c32ba9cc7cb0335e7c320179e2689ab59bba6
Reviewed-on: https://chromium-review.googlesource.com/957918Reviewed-by: Ken Rockot <rockot@chromium.org>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Commit-Queue: Helen Li <xunjieli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550477}

content/browser/renderer_host/clipboard_host_impl_unittest.cc

@@ -103,15 +103,4 @@ TEST_F(ClipboardHostImplTest, ImageSizeOverflows32BitRowBytes) {
             clipboard()->GetSequenceNumber(ui::CLIPBOARD_TYPE_COPY_PASTE));
 }
 
-TEST_F(ClipboardHostImplTest, InvalidSharedMemoryHandle) {
-  mojo::ScopedSharedBufferHandle shared_memory;
-  CallWriteImage(gfx::Size(5, 5), std::move(shared_memory), 0);
-  uint64_t sequence_number =
-      clipboard()->GetSequenceNumber(ui::CLIPBOARD_TYPE_COPY_PASTE);
-  CallCommitWrite();
-
-  EXPECT_EQ(sequence_number,
-            clipboard()->GetSequenceNumber(ui::CLIPBOARD_TYPE_COPY_PASTE));
-}
-
 }  // namespace content

mojo/public/cpp/system/handle.h

@@ -94,7 +94,10 @@ class ScopedHandleBase {
   }
 
   const HandleType& get() const { return handle_; }
-  const HandleType* operator->() const { return &handle_; }
+  const HandleType* operator->() const {
+    DCHECK(handle_.is_valid());
+    return &handle_;
+  }
 
   template <typename PassedHandleType>
   static ScopedHandleBase<HandleType> From(