Limit renderer saved frames to avoid running out of fds.

content/browser/renderer_host/renderer_frame_manager.cc

Index: content/browser/renderer_host/renderer_frame_manager.cc
diff --git a/content/browser/renderer_host/renderer_frame_manager.cc b/content/browser/renderer_host/renderer_frame_manager.cc
index 15c9814d61075f032ec5d3196f6eec2071c573d5..8ad31c42fb61609b8e435562acb93450573c22a2 100644
--- a/content/browser/renderer_host/renderer_frame_manager.cc
+++ b/content/browser/renderer_host/renderer_frame_manager.cc
@@ -7,7 +7,9 @@
 #include <algorithm>
 
 #include "base/logging.h"
+#include "base/memory/shared_memory.h"
 #include "base/sys_info.h"
+#include "content/common/host_shared_bitmap_manager.h"
 
 namespace content {
 
@@ -71,9 +73,23 @@ RendererFrameManager::RendererFrameManager() {
 RendererFrameManager::~RendererFrameManager() {}
 
 void RendererFrameManager::CullUnlockedFrames() {
+  uint32 saved_frame_limit = max_number_of_saved_frames();
+
+  if (saved_frame_limit > 2) {
+    // Reduce the number of saved frames to attempt to limit browser to using at
+    // most 1/8 of the available shared memory handles. This is only a soft
+    // limit, and it may go over as necessary.
+    const float kHandleMaxFraction = 1 / 8.0f;
+    float memory_handle_fraction =
+        HostSharedBitmapManager::current()->AllocatedBitmapCount() * 1.0f /
+        base::SharedMemory::GetHandleLimit();
+    float fraction_to_reduce =
+        std::min(1.0f, memory_handle_fraction / kHandleMaxFraction);
+    saved_frame_limit -=
+        static_cast<uint32>((saved_frame_limit - 2) * fraction_to_reduce);

[piman, 2014/04/23 00:32:02]

I'm not sure I agree with this computation. If we're right at the handle limit
with 5 frames and max_number_of_saved_frames() == 5, we'll end up with
saved_frame_limit==2, so we'll discard frames even though we fit.

How about something like:
int max_handles = base::SharedMemory::GetHandleLimit() * kHandleMaxFraction; 
(it's actually a constant, could be done in constructor)
int handles_per_frame =
HostSharedBitmapManager::current()->AllocatedBitmapCount() /
(unlocked_frames_.size() + locked_frames_.size())
int saved_frame_limit = std::max(1, std::min(max_number_of_saved_frames(),
max_handles/handles_per_frame))

+  }

[piman, 2014/04/23 00:32:02]

RenderWidgetHostViewAuraTest.DiscardDelegatedFrames/DiscardDelegatedFramesWithLocking
test current behavior, they'll have to be modified (ideally, extended to take
this into account).

   while (!unlocked_frames_.empty() &&
-         unlocked_frames_.size() + locked_frames_.size() >
-             max_number_of_saved_frames()) {
+         unlocked_frames_.size() + locked_frames_.size() > saved_frame_limit) {
     size_t old_size = unlocked_frames_.size();
     // Should remove self from list.
     unlocked_frames_.back()->EvictCurrentFrame();