Replace web_cache_messages.h with Mojo service.

components/web_cache/public/interfaces/web_cache.mojom

Index: components/web_cache/public/interfaces/web_cache.mojom
diff --git a/components/web_cache/public/interfaces/web_cache.mojom b/components/web_cache/public/interfaces/web_cache.mojom
new file mode 100644
index 0000000000000000000000000000000000000000..64af4fc343d29addad821cac8c82bdf8c7ac240d
--- /dev/null
+++ b/components/web_cache/public/interfaces/web_cache.mojom
@@ -0,0 +1,14 @@
+// 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 WebCache {
+  // Set cache capacity values.
+  SetCacheCapacities(uint64 min_dead_capacity,
+                     uint64 max_dead_capacity,
+                     uint64 capacity);
+  // Clear cache.
+  ClearCache(bool on_navigation);
+};