Revert of discardable_memory: Using mojo IPC to replace Chrome IPC

components/discardable_memory/service/discardable_shared_memory_manager.cc

Index: components/discardable_memory/service/discardable_shared_memory_manager.cc
diff --git a/components/discardable_memory/service/discardable_shared_memory_manager.cc b/components/discardable_memory/service/discardable_shared_memory_manager.cc
index 6f5bf1cf2ec0088ec54282df7e9c659ea079f167..1036dc84d697ed5324d2f181a15b7b618cdddf46 100644
--- a/components/discardable_memory/service/discardable_shared_memory_manager.cc
+++ b/components/discardable_memory/service/discardable_shared_memory_manager.cc
@@ -29,8 +29,6 @@
 #include "base/trace_event/trace_event.h"
 #include "build/build_config.h"
 #include "components/discardable_memory/common/discardable_shared_memory_heap.h"
-#include "mojo/public/cpp/bindings/strong_binding.h"
-#include "mojo/public/cpp/system/platform_handle.h"
 
 #if defined(OS_LINUX)
 #include "base/files/file_path.h"
@@ -58,48 +56,6 @@
              reinterpret_cast<const char*>(&client_id), sizeof(client_id))) +
          1;
 }
-
-// mojom::DiscardableSharedMemoryManager implementation. It contains the
-// |client_id_| which is not visible to client. We associate allocations with a
-// given mojo instance, so if the instance is closed, we can release the
-// allocations associated with that instance.
-class MojoDiscardableSharedMemoryManagerImpl
-    : public mojom::DiscardableSharedMemoryManager {
- public:
-  MojoDiscardableSharedMemoryManagerImpl(
-      int32_t client_id,
-      ::discardable_memory::DiscardableSharedMemoryManager* manager)
-      : client_id_(client_id), manager_(manager) {}
-
-  ~MojoDiscardableSharedMemoryManagerImpl() override {
-    // Remove this client from the |manager_|, so all allocated discardable
-    // memory belong to this client will be released.
-    manager_->ClientRemoved(client_id_);
-  }
-
-  // mojom::DiscardableSharedMemoryManager overrides:
-  void AllocateLockedDiscardableSharedMemory(
-      uint32_t size,
-      int32_t id,
-      const AllocateLockedDiscardableSharedMemoryCallback& callback) override {
-    base::SharedMemoryHandle handle;
-    manager_->AllocateLockedDiscardableSharedMemoryForClient(client_id_, size,
-                                                             id, &handle);
-    mojo::ScopedSharedBufferHandle memory =
-        mojo::WrapSharedMemoryHandle(handle, size, false /* read_only */);
-    return callback.Run(std::move(memory));
-  }
-
-  void DeletedDiscardableSharedMemory(int32_t id) override {
-    manager_->ClientDeletedDiscardableSharedMemory(id, client_id_);
-  }
-
- private:
-  const int32_t client_id_;
-  ::discardable_memory::DiscardableSharedMemoryManager* const manager_;
-
-  DISALLOW_COPY_AND_ASSIGN(MojoDiscardableSharedMemoryManagerImpl);
-};
 
 class DiscardableMemoryImpl : public base::DiscardableMemory {
  public:
@@ -224,8 +180,7 @@
 DiscardableSharedMemoryManager::MemorySegment::~MemorySegment() {}
 
 DiscardableSharedMemoryManager::DiscardableSharedMemoryManager()
-    : next_client_id_(1),
-      default_memory_limit_(GetDefaultMemoryLimit()),
+    : default_memory_limit_(GetDefaultMemoryLimit()),
       memory_limit_(default_memory_limit_),
       bytes_allocated_(0),
       memory_pressure_listener_(new base::MemoryPressureListener(
@@ -250,38 +205,23 @@
       this);
 }
 
-// static
-DiscardableSharedMemoryManager*
-DiscardableSharedMemoryManager::CreateInstance() {
-  DCHECK(g_discardable_shared_memory_manager == nullptr);
+DiscardableSharedMemoryManager* DiscardableSharedMemoryManager::current() {
   return g_discardable_shared_memory_manager.Pointer();
-}
-
-// static
-DiscardableSharedMemoryManager* DiscardableSharedMemoryManager::GetInstance() {
-  DCHECK(!(g_discardable_shared_memory_manager == nullptr));
-  return g_discardable_shared_memory_manager.Pointer();
-}
-
-void DiscardableSharedMemoryManager::Bind(
-    mojom::DiscardableSharedMemoryManagerRequest request) {
-  mojo::MakeStrongBinding(
-      base::MakeUnique<MojoDiscardableSharedMemoryManagerImpl>(
-          next_client_id_++, this),
-      std::move(request));
 }
 
 std::unique_ptr<base::DiscardableMemory>
 DiscardableSharedMemoryManager::AllocateLockedDiscardableMemory(size_t size) {
   DCHECK_NE(size, 0u);
 
-  int32_t new_id = g_next_discardable_shared_memory_id.GetNext();
+  DiscardableSharedMemoryId new_id =
+      g_next_discardable_shared_memory_id.GetNext();
+  base::ProcessHandle current_process_handle = base::GetCurrentProcessHandle();
 
   // Note: Use DiscardableSharedMemoryHeap for in-process allocation
   // of discardable memory if the cost of each allocation is too high.
   base::SharedMemoryHandle handle;
-  AllocateLockedDiscardableSharedMemory(kInvalidUniqueClientID, size, new_id,
-                                        &handle);
+  AllocateLockedDiscardableSharedMemory(
+      current_process_handle, kInvalidUniqueClientID, size, new_id, &handle);
   std::unique_ptr<base::DiscardableSharedMemory> memory(
       new base::DiscardableSharedMemory(handle));
   if (!memory->Map(size))
@@ -368,16 +308,17 @@
 
 void DiscardableSharedMemoryManager::
     AllocateLockedDiscardableSharedMemoryForClient(
+        base::ProcessHandle process_handle,
         int client_id,
         size_t size,
-        int32_t id,
+        DiscardableSharedMemoryId id,
         base::SharedMemoryHandle* shared_memory_handle) {
-  AllocateLockedDiscardableSharedMemory(client_id, size, id,
+  AllocateLockedDiscardableSharedMemory(process_handle, client_id, size, id,
                                         shared_memory_handle);
 }
 
 void DiscardableSharedMemoryManager::ClientDeletedDiscardableSharedMemory(
-    int32_t id,
+    DiscardableSharedMemoryId id,
     int client_id) {
   DeletedDiscardableSharedMemory(id, client_id);
 }
@@ -439,9 +380,10 @@
 }
 
 void DiscardableSharedMemoryManager::AllocateLockedDiscardableSharedMemory(
+    base::ProcessHandle process_handle,
     int client_id,
     size_t size,
-    int32_t id,
+    DiscardableSharedMemoryId id,
     base::SharedMemoryHandle* shared_memory_handle) {
   base::AutoLock lock(lock_);
 
@@ -474,6 +416,15 @@
     return;
   }
 
+  if (!memory->ShareToProcess(process_handle, shared_memory_handle)) {
+    LOG(ERROR) << "Cannot share discardable memory segment";
+    *shared_memory_handle = base::SharedMemory::NULLHandle();
+    return;
+  }
+
+  // Close file descriptor to avoid running out.
+  memory->Close();
+
   base::CheckedNumeric<size_t> checked_bytes_allocated = bytes_allocated_;
   checked_bytes_allocated += memory->mapped_size();
   if (!checked_bytes_allocated.IsValid()) {
@@ -484,10 +435,6 @@
   bytes_allocated_ = checked_bytes_allocated.ValueOrDie();
   BytesAllocatedChanged(bytes_allocated_);
 
-  *shared_memory_handle = base::SharedMemory::DuplicateHandle(memory->handle());
-  // Close file descriptor to avoid running out.
-  memory->Close();
-
   scoped_refptr<MemorySegment> segment(new MemorySegment(std::move(memory)));
   client_segments[id] = segment.get();
   segments_.push_back(segment.get());
@@ -498,7 +445,7 @@
 }
 
 void DiscardableSharedMemoryManager::DeletedDiscardableSharedMemory(
-    int32_t id,
+    DiscardableSharedMemoryId id,
     int client_id) {
   base::AutoLock lock(lock_);