mediaview: Implement FakeFileSystemInstance.

components/arc/test/fake_file_system_instance.h

Index: components/arc/test/fake_file_system_instance.h
diff --git a/components/arc/test/fake_file_system_instance.h b/components/arc/test/fake_file_system_instance.h
index 5fa4ac8032ed192352d3d252f12a5f30b2a78855..a019368f3aec65185263d009ff78033efa5bc2e3 100644
--- a/components/arc/test/fake_file_system_instance.h
+++ b/components/arc/test/fake_file_system_instance.h
@@ -8,6 +8,7 @@
 #include <stdint.h>
 
 #include <map>
+#include <set>
 #include <string>
 #include <utility>
 #include <vector>
@@ -102,12 +103,20 @@ class FakeFileSystemInstance : public mojom::FileSystemInstance {
   FakeFileSystemInstance();
   ~FakeFileSystemInstance() override;
 
+  // Returns true if Init() has been called.
+  bool InitCalled();
+
   // Adds a file accessible by content URL based methods.
   void AddFile(const File& file);
 
   // Adds a document accessible by document provider based methods.
   void AddDocument(const Document& document);
 
+  // Triggers watchers installed to a document.
+  void TriggerWatchers(const std::string& authority,
+                       const std::string& document_id,
+                       mojom::ChangeType type);
+
   // mojom::FileSystemInstance:
   void AddWatcher(const std::string& authority,
                   const std::string& document_id,
@@ -136,6 +145,8 @@ class FakeFileSystemInstance : public mojom::FileSystemInstance {
 
   base::ScopedTempDir temp_dir_;
 
+  mojom::FileSystemHostPtr host_;
+
   // Mapping from a content URL to a file.
   std::map<std::string, File> files_;
 
@@ -145,6 +156,14 @@ class FakeFileSystemInstance : public mojom::FileSystemInstance {
   // Mapping from a document key to its child documents.
   std::map<DocumentKey, std::vector<DocumentKey>> child_documents_;
 
+  // Mapping from a document key to its watchers.
+  std::map<DocumentKey, std::set<int64_t>> document_to_watchers_;
+
+  // Mapping from a watcher ID to a document key.
+  std::map<int64_t, DocumentKey> watcher_to_document_;
+
+  int64_t next_watcher_id_ = 1;
+
   DISALLOW_COPY_AND_ASSIGN(FakeFileSystemInstance);
 };