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

blimp/common/blob_cache/in_memory_blob_cache_unittest.cc

Index: blimp/common/blob_cache/in_memory_blob_cache_unittest.cc
diff --git a/blimp/common/blob_cache/in_memory_blob_cache_unittest.cc b/blimp/common/blob_cache/in_memory_blob_cache_unittest.cc
index 9cc24d71d13e4b88a0422677d63b54040f8c749a..431f8eb05cd4a8bf33521cdb9d84fa274c8e2211 100644
--- a/blimp/common/blob_cache/in_memory_blob_cache_unittest.cc
+++ b/blimp/common/blob_cache/in_memory_blob_cache_unittest.cc
@@ -44,6 +44,10 @@ TEST_F(InMemoryBlobCacheTest, SimplePutContainsAndGetOperations) {
   BlobDataPtr out = cache_.Get(kFoo);
 
   EXPECT_EQ(blob_data, out);
+
+  auto cache_state = cache_.GetCachedBlobIds();
+  EXPECT_EQ(1u, cache_state.size());
+  EXPECT_EQ(kFoo, cache_state[0]);
 }
 
 TEST_F(InMemoryBlobCacheTest, TestDuplicatePut) {
@@ -59,6 +63,10 @@ TEST_F(InMemoryBlobCacheTest, TestDuplicatePut) {
   cache_.Put(kFoo, duplicate);
   BlobDataPtr out2 = cache_.Get(kFoo);
   EXPECT_EQ(first, out2);
+
+  auto cache_state = cache_.GetCachedBlobIds();
+  EXPECT_EQ(1u, cache_state.size());
+  EXPECT_EQ(kFoo, cache_state[0]);
 }
 
 }  // namespace