Replace web_cache_messages.h with Mojo service.

components/web_cache/public/interfaces/web_cache_service.mojom

Index: components/web_cache/public/interfaces/web_cache_service.mojom
diff --git a/components/web_cache/public/interfaces/web_cache_service.mojom b/components/web_cache/public/interfaces/web_cache_service.mojom
new file mode 100644
index 0000000000000000000000000000000000000000..3925f9e07f41eb97e95be7553e96ab8ee9d80309
--- /dev/null
+++ b/components/web_cache/public/interfaces/web_cache_service.mojom
@@ -0,0 +1,16 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+module web_cache.mojom;
+
+interface WebCacheService {
+  // Set cache capacity values.
+  // Each call is independent, overlapping calls are possible.

[Anand Mistry (off Chromium), 2016/02/18 12:33:57]

I don't understand this comment. These are all one-way messages, and an
interface provides strict ordering of calls. I can't see how overlap is relevant
here.

[leonhsl(Using Gerrit), 2016/02/19 08:37:41]

Yeah I think you're right, this interface has no such worry. Removed this
comment.

+  SetCacheCapacities(uint64 min_dead_capacity,
+                     uint64 max_dead_capacity,
+                     uint64 capacity);
+  // Clear cache.
+  // Each call is independent, overlapping calls are possible.
+  ClearCache(bool on_navigation);
+};