TrimMemory strategy while offscreenPreRaster is on.

android_webview/browser/browser_view_renderer.cc

Index: android_webview/browser/browser_view_renderer.cc
diff --git a/android_webview/browser/browser_view_renderer.cc b/android_webview/browser/browser_view_renderer.cc
index 7e229bc2f8c534ba41fde486c64ea8f276483d5f..8121a753b48acbb0d691b6e240a64aa9df9a0418 100644
--- a/android_webview/browser/browser_view_renderer.cc
+++ b/android_webview/browser/browser_view_renderer.cc
@@ -118,7 +118,6 @@ 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.
@@ -145,7 +144,8 @@ void BrowserViewRenderer::TrimMemory(const int level, const bool visible) {
 
   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;
@@ -153,8 +153,8 @@ void BrowserViewRenderer::TrimMemory(const int level, const bool visible) {
 
   // 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() {
@@ -337,7 +337,9 @@ void BrowserViewRenderer::ClearView() {
 }
 
 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;
 }