Add Mojo IPC for seeding new Renderer with Browser's cached blob state.

blimp/common/blob_cache/in_memory_blob_cache.cc

Index: blimp/common/blob_cache/in_memory_blob_cache.cc
diff --git a/blimp/common/blob_cache/in_memory_blob_cache.cc b/blimp/common/blob_cache/in_memory_blob_cache.cc
index bad46df059937c7849f89da6a897de8e93114612..55718ba59a39cc38efb86006f8cff939cd95dc3f 100644
--- a/blimp/common/blob_cache/in_memory_blob_cache.cc
+++ b/blimp/common/blob_cache/in_memory_blob_cache.cc
@@ -12,6 +12,14 @@ InMemoryBlobCache::InMemoryBlobCache() {}
 
 InMemoryBlobCache::~InMemoryBlobCache() {}
 
+std::vector<BlobId> InMemoryBlobCache::GetCachedBlobIds() const {
+  std::vector<BlobId> output;

[Wez, 2016/07/01 00:30:20]

nit: Suggest cached_ids.

[Kevin M, 2016/07/18 16:58:16]

Done.

+  for (const auto& pair : cache_) {

[Wez, 2016/07/01 00:30:20]

nit: Suggest blob_id_and_data_pair for clarity (since you are using auto, so the
type is not immediately clear without jumping to the header).

[Kevin M, 2016/07/18 16:58:16]

Done.

+    output.push_back(pair.first);
+  }
+  return output;
+}
+
 void InMemoryBlobCache::Put(const BlobId& id, BlobDataPtr data) {
   if (Contains(id)) {
     // In cases where the engine has miscalculated what is already available