Add ScopedSurfaceRequestManager

content/browser/android/scoped_surface_request_manager.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "content/browser/android/scoped_surface_request_manager.h"
+
+#include "base/base64.h"
+#include "content/public/browser/browser_thread.h"
+#include "crypto/random.h"
+
+namespace content {
+
+const int kRequestTokenSize = 16;
+// 128 bits / (6 bits per base64 char) = 22.33 chars, or 24 chars with padding.
+const size_t kPaddedStringTokenSize = 24;
+
+// static
+ScopedSurfaceRequestManager* ScopedSurfaceRequestManager::GetInstance() {
+  return base::Singleton<
+      ScopedSurfaceRequestManager,
+      base::LeakySingletonTraits<ScopedSurfaceRequestManager>>::get();
+}
+
+std::string ScopedSurfaceRequestManager::RegisterScopedSurfaceRequest(
+    ScopedSurfaceRequestCB request_cb) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  DCHECK(!request_cb.is_null());
+
+  std::string request_token = GetBase64UnguessableToken();
+
+  DCHECK(!request_callbacks_.count(request_token));
+  request_callbacks_.insert(std::make_pair(request_token, request_cb));
+
+  return request_token;
+}
+
+void ScopedSurfaceRequestManager::UnregisterScopedSurfaceRequest(
+    std::string request_token) {

[dcheng, 2016/09/09 20:51:08]

Strings (with few exceptions) should be passed by const ref.

+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  GetAndUnregisterInternal(request_token);
+}
+
+ScopedSurfaceRequestManager::ScopedSurfaceRequestCB
+ScopedSurfaceRequestManager::GetAndUnregisterInternal(
+    std::string request_token) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  DCHECK(kPaddedStringTokenSize == request_token.length());

[dcheng, 2016/09/09 20:51:07]

Nit: DCHECK_EQ, but this is not a safe assumption, since this token can come
from a less trusted process, no?

+
+  ScopedSurfaceRequestManager::ScopedSurfaceRequestCB request;
+
+  auto it = request_callbacks_.find(request_token);
+  if (it != request_callbacks_.end()) {
+    request = it->second;
+    request_callbacks_.erase(it);
+  }
+
+  return request;
+}
+
+void ScopedSurfaceRequestManager::ForwardSurfaceTextureForSurfaceRequest(
+    std::string request_token,
+    gl::SurfaceTexture* surface_texture) {
+  gl::ScopedJavaSurface surface(surface_texture);
+  FulfillScopedSurfaceRequest(request_token, std::move(surface));
+}
+
+void ScopedSurfaceRequestManager::FulfillScopedSurfaceRequest(
+    std::string request_token,
+    gl::ScopedJavaSurface surface) {
+  if (!BrowserThread::CurrentlyOn(BrowserThread::UI)) {
+    // base::Unretained is safe because the lifetime of this object is tied to
+    // the lifetime of the browser process.
+    BrowserThread::PostTask(
+        BrowserThread::UI, FROM_HERE,
+        base::Bind(&ScopedSurfaceRequestManager::FulfillScopedSurfaceRequest,
+                   base::Unretained(this), request_token,
+                   base::Passed(std::move(surface))));
+    return;
+  }
+
+  ScopedSurfaceRequestManager::ScopedSurfaceRequestCB request =
+      GetAndUnregisterInternal(request_token);
+
+  if (!request.is_null())
+    request.Run(std::move(surface));
+}
+
+std::string ScopedSurfaceRequestManager::GetBase64UnguessableToken() {
+  char token_bits[kRequestTokenSize];
+  crypto::RandBytes(token_bits, sizeof(token_bits));
+
+  std::string result;
+  base::Base64Encode(base::StringPiece(token_bits, kRequestTokenSize), &result);
+  return result;
+}
+
+ScopedSurfaceRequestManager::ScopedSurfaceRequestManager() {}
+
+ScopedSurfaceRequestManager::~ScopedSurfaceRequestManager() {}
+
+}  // namespace content