TrimMemory strategy while offscreenPreRaster is on.

android_webview/browser/browser_view_renderer.cc

 // Copyright 2014 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/browser_view_renderer.h"
 
 #include "android_webview/browser/browser_view_renderer_client.h"
 #include "android_webview/browser/child_frame.h"
 #include "base/auto_reset.h"
 #include "base/command_line.h"
@@ skipping 100 matching lines @@
 }
 
 SharedRendererState* BrowserViewRenderer::GetAwDrawGLViewContext() {
   return &shared_renderer_state_;
 }
 
 bool BrowserViewRenderer::RequestDrawGL(bool wait_for_completion) {
   return client_->RequestDrawGL(wait_for_completion);
 }
 
-// This function updates the resource allocation in GlobalTileManager.
 void BrowserViewRenderer::TrimMemory(const int level, const bool visible) {
   DCHECK(ui_task_runner_->BelongsToCurrentThread());
   // Constants from Android ComponentCallbacks2.
   enum {
     TRIM_MEMORY_RUNNING_LOW = 10,
     TRIM_MEMORY_UI_HIDDEN = 20,
     TRIM_MEMORY_BACKGROUND = 40,
     TRIM_MEMORY_MODERATE = 60,
   };
 
   // Not urgent enough. TRIM_MEMORY_UI_HIDDEN is treated specially because
   // it does not indicate memory pressure, but merely that the app is
   // backgrounded.
   if (level < TRIM_MEMORY_RUNNING_LOW || level == TRIM_MEMORY_UI_HIDDEN)
     return;
 
   // Do not release resources on view we expect to get DrawGL soon.
   if (level < TRIM_MEMORY_BACKGROUND && visible)
     return;
 
   // Nothing to drop.
   if (!compositor_ || !hardware_enabled_)
     return;
 
   TRACE_EVENT0("android_webview", "BrowserViewRenderer::TrimMemory");
 
-  // Drop everything in hardware.
+  // If offscreen pre-raster is disabled, drop everything in hardware. Otherwise
+  // keep the tiles and just delete the HardwareRenderer.
   if (level >= TRIM_MEMORY_MODERATE) {
     shared_renderer_state_.ReleaseHardwareDrawIfNeededOnUI();
     return;
   }
 
   // Just set the memory limit to 0 and drop all tiles. This will be reset to
   // normal levels in the next DrawGL call.
-  compositor_->SetMemoryPolicy(0u);
-  ForceFakeCompositeSW();
+  if (!offscreen_pre_raster_)
+    compositor_->SetMemoryPolicy(0u);
 }
 
 size_t BrowserViewRenderer::CalculateDesiredMemoryPolicy() {
   if (g_memory_override_in_bytes)
     return static_cast<size_t>(g_memory_override_in_bytes);
 
   gfx::Rect interest_rect = offscreen_pre_raster_
                                 ? gfx::Rect(size_)
                                 : last_on_draw_global_visible_rect_;
   size_t width = interest_rect.width();
@@ skipping 162 matching lines @@
                        TRACE_EVENT_SCOPE_THREAD);
   if (clear_view_)
     return;
 
   clear_view_ = true;
   // Always invalidate ignoring the compositor to actually clear the webview.
   PostInvalidateWithFallback();
 }
 
 void BrowserViewRenderer::SetOffscreenPreRaster(bool enable) {
-  // TODO(hush): anything to do when the setting is toggled?
+  if (offscreen_pre_raster_ != enable && compositor_)
+    compositor_->SetMemoryPolicy(CalculateDesiredMemoryPolicy());

[boliu, 2015/04/15 00:31:01]

This ignores hardware_enabled_

[hush (inactive), 2015/04/15 21:35:48]

What do you mean? Do I need to do anything here? Do you mean only calling this
method when hardware is enabled?

[boliu, 2015/04/15 22:27:45]

policy should be 0 if hardware_enabled_ is false, this will set it to > 0 if
called when webview is not hardware_enabled

[boliu, 2015/04/15 22:57:04]

Maybe CalcuateDesiredMemoryPolicy should take into account hardware_enabled_,
and directly call SetMemoryPolicy. Then it can be renamed to something like
"UpdateMemoryPolicy"

[hush (inactive), 2015/04/16 01:13:24]

I agree doing so keeps the logic sane. But setting the memory policy to non-zero
when hardware is not enabled will not cause any bugs, right? (as long as you
have the right memory policy when hardware is enabled.)

+
   offscreen_pre_raster_ = enable;
 }
 
 void BrowserViewRenderer::SetIsPaused(bool paused) {
   TRACE_EVENT_INSTANT1("android_webview",
                        "BrowserViewRenderer::SetIsPaused",
                        TRACE_EVENT_SCOPE_THREAD,
                        "paused",
                        paused);
   is_paused_ = paused;
@@ skipping 362 matching lines @@
   base::StringAppendF(&str,
                       "overscroll_rounding_error_: %s ",
                       overscroll_rounding_error_.ToString().c_str());
   base::StringAppendF(
       &str, "on_new_picture_enable: %d ", on_new_picture_enable_);
   base::StringAppendF(&str, "clear_view: %d ", clear_view_);
   return str;
 }
 
 }  // namespace android_webview