[Android WebView] OnMemoryPressure to drop tile memory

android_webview/browser/in_process_view_renderer.cc

 // Copyright 2013 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 "android_webview/browser/in_process_view_renderer.h"
 
 #include <android/bitmap.h>
 
 #include "android_webview/browser/aw_gl_surface.h"
 #include "android_webview/browser/scoped_app_gl_state_restore.h"
@@ skipping 298 matching lines @@
   std::stringstream size;
   size << default_tile_size;
   cl->AppendSwitchASCII(switches::kDefaultTileWidth, size.str());
   cl->AppendSwitchASCII(switches::kDefaultTileHeight, size.str());
 }
 
 bool InProcessViewRenderer::RequestProcessGL() {
   return client_->RequestDrawGL(NULL);
 }
 
+void InProcessViewRenderer::OnMemoryPressure(
+    base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level) {
+  // Nothing to release.
+  if (!attached_to_window_ || !compositor_ || !hardware_initialized_)
+    return;
+
+  // Do not release resources on view we expect to get DrawGL soon.
+  client_->UpdateGlobalVisibleRect();
+  if (view_visible_ && window_visible_ &&
+      !cached_global_visible_rect_.IsEmpty()) {
+    return;
+  }
+
+  // Check that the expected EGL context is current. This may not be the case if
+  // the OnMemoryPressure callback is triggered manually in Chromium code.
+  DCHECK(last_egl_context_);
+  if (eglGetCurrentContext() != last_egl_context_)

[boliu, 2013/10/01 20:10:48]

This check is failing, so as is, this patch does nothing. Looking at why.

+    return;
+
+  TRACE_EVENT0("android_webview", "OnMemoryPressure");
+  ScopedAppGLStateRestore state_restore(ScopedAppGLStateRestore::MODE_ON_TRIM);
+  gpu::InProcessCommandBuffer::ProcessGpuWorkOnCurrentThread();
+  ScopedAllowGL allow_gl;
+
+  // Just set the memory limit to 0 and drop all tiles. This will be reset to
+  // normal levels in the next DrawGL call.
+  content::SynchronousCompositorMemoryPolicy policy;
+  policy.bytes_limit = 0;
+  policy.num_resources_limit = 0;
+  compositor_->SetMemoryPolicy(policy);
+}
+
 void InProcessViewRenderer::UpdateCachedGlobalVisibleRect() {
   client_->UpdateGlobalVisibleRect();
 }
 
 bool InProcessViewRenderer::OnDraw(jobject java_canvas,
                                    bool is_hardware_canvas,
                                    const gfx::Vector2d& scroll,
                                    const gfx::Rect& clip) {
   scroll_at_start_of_frame_  = scroll;
   if (is_hardware_canvas && attached_to_window_ && HardwareEnabled()) {
     // We should be performing a hardware draw here. If we don't have the
     // comositor yet or if RequestDrawGL fails, it means we failed this draw and
     // thus return false here to clear to background color for this draw.
     return compositor_ && client_->RequestDrawGL(java_canvas);
   }
   // Perform a software draw
   return DrawSWInternal(java_canvas, clip);
 }
 
 bool InProcessViewRenderer::InitializeHwDraw() {
   TRACE_EVENT0("android_webview", "InitializeHwDraw");
   DCHECK(!gl_surface_);
   gl_surface_  = new AwGLSurface;
   hardware_failed_ = !compositor_->InitializeHwDraw(gl_surface_);
   hardware_initialized_ = true;
 
-  if (hardware_failed_)
+  if (hardware_failed_) {
     gl_surface_ = NULL;
+  } else {
+    memory_pressure_listener_.reset(new base::MemoryPressureListener(
+        base::Bind(&InProcessViewRenderer::OnMemoryPressure,
+                   base::Unretained(this))));
+  }
 
   return !hardware_failed_;
 }
 
 void InProcessViewRenderer::DrawGL(AwDrawGLInfo* draw_info) {
   TRACE_EVENT0("android_webview", "InProcessViewRenderer::DrawGL");
 
   manager_key_ = g_view_renderer_manager.Get().DidDrawGL(manager_key_, this);
 
   // We need to watch if the current Android context has changed and enforce
@@ skipping 279 matching lines @@
   NoLongerExpectsDrawGL();
   if (hardware_initialized_) {
     DCHECK(compositor_);
 
     ScopedAppGLStateRestore state_restore(
         ScopedAppGLStateRestore::MODE_DETACH_FROM_WINDOW);
     gpu::InProcessCommandBuffer::ProcessGpuWorkOnCurrentThread();
     ScopedAllowGL allow_gl;
     compositor_->ReleaseHwDraw();
     hardware_initialized_ = false;
+    memory_pressure_listener_.reset();
   }
 
   gl_surface_ = NULL;
   attached_to_window_ = false;
 }
 
 bool InProcessViewRenderer::IsAttachedToWindow() {
   return attached_to_window_;
 }
 
@@ skipping 269 matching lines @@
     base::StringAppendF(&str,
                         "surface width height: [%d %d] ",
                         draw_info->width,
                         draw_info->height);
     base::StringAppendF(&str, "is_layer: %d ", draw_info->is_layer);
   }
   return str;
 }
 
 }  // namespace android_webview