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 a717d960d1555ce040022d0aed73dcdad23d652d..d51c9249b7afe8046b5de7d6faeeef98222a35d5 100644
--- a/blimp/engine/mojo/blob_channel_service.cc
+++ b/blimp/engine/mojo/blob_channel_service.cc
@@ -4,8 +4,12 @@
 
 #include "blimp/engine/mojo/blob_channel_service.h"
 
+#include <string>
+#include <unordered_map>
 #include <utility>
+#include <vector>
 
+#include "base/memory/ptr_util.h"
 #include "blimp/net/blob_channel/blob_channel_sender.h"
 #include "mojo/public/cpp/system/buffer.h"
 
@@ -21,7 +25,17 @@ BlobChannelService::BlobChannelService(BlobChannelSender* blob_channel_sender,
 
 BlobChannelService::~BlobChannelService() {}
 
-void BlobChannelService::PutBlob(const mojo::String& id,
+void BlobChannelService::GetCachedBlobIds(
+    const BlobChannelService::GetCachedBlobIdsCallback& response_callback) {
+  VLOG(1) << "BlobChannel::GetCachedBlobIds called.";
+  std::unordered_map<std::string, bool> cache_state;
+  for (const auto& next_entry : blob_channel_sender_->GetCachedBlobIds()) {
+    cache_state[next_entry.id] = next_entry.was_delivered;
+  }
+  response_callback.Run(std::move(cache_state));
+}
+
+void BlobChannelService::PutBlob(const std::string& id,
                                  mojo::ScopedSharedBufferHandle data,
                                  uint32_t size) {
   // Map |data| into the address space and copy out its contents.
@@ -43,7 +57,7 @@ void BlobChannelService::PutBlob(const mojo::String& id,
   blob_channel_sender_->PutBlob(id, std::move(new_blob));
 }
 
-void BlobChannelService::DeliverBlob(const mojo::String& id) {
+void BlobChannelService::DeliverBlob(const std::string& id) {
   blob_channel_sender_->DeliverBlob(id);
 }