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

blimp/engine/mojo/blob_channel_service.cc

Index: blimp/engine/mojo/blob_channel_service.cc
diff --git a/blimp/engine/mojo/blob_channel_service.cc b/blimp/engine/mojo/blob_channel_service.cc
index 0234df60698b3a2c2628537b7e66cfd9ae44bfd9..413c19c94de269c54f7ee6143ba15ecbb69182a2 100644
--- a/blimp/engine/mojo/blob_channel_service.cc
+++ b/blimp/engine/mojo/blob_channel_service.cc
@@ -4,6 +4,8 @@
 
 #include "blimp/engine/mojo/blob_channel_service.h"
 
+#include <vector>
+
 #include "blimp/net/blob_channel/blob_channel_sender.h"
 
 namespace blimp {
@@ -18,6 +20,23 @@ BlobChannelService::BlobChannelService(BlobChannelSender* blob_channel_sender,
 
 BlobChannelService::~BlobChannelService() {}
 
+void BlobChannelService::GetCachedBlobIds(
+    const BlobChannelService::GetCachedBlobIdsCallback& callback) {
+  VLOG(1) << "BlobChannel::GetCachedBlobIds called.";
+
+  // Pass the Mojo representation of the cache state to |callback|.
+  std::vector<BlobChannelSender::CacheStateEntry> cache_state =
+      blob_channel_sender_->GetCachedBlobIds();
+  auto output = mojo::Array<mojom::CacheStateEntryPtr>::New(cache_state.size());
+  for (size_t i = 0; i < cache_state.size(); ++i) {
+    mojom::CacheStateEntryPtr converted(mojom::CacheStateEntry::New());
+    converted->id.Swap(&cache_state[i].id);
+    converted->was_delivered = cache_state[i].was_delivered;

[dcheng, 2016/06/25 00:55:55]

Would it make sense to write a typemap for this rather than marshalling this
manually?

+    output[i] = std::move(converted);
+  }
+  callback.Run(std::move(output));
+}
+
 void BlobChannelService::PutBlob(const mojo::String& id,
                                  const mojo::String& data) {
   blob_channel_sender_->PutBlob(id, new BlobData(data));