Fix RenderWidgetHostViewAuraTest failure on devices with little memory

This test fails (same symptoms as bug 443352) on hardware with <= 256MB
of RAM.

BUG= internal b/21093117

Review URL: https://codereview.chromium.org/1140813005

Cr-Commit-Position: refs/heads/master@{#330541}

content/browser/renderer_host/render_widget_host_view_aura_unittest.cc

@@ -2048,10 +2048,14 @@ TEST_F(RenderWidgetHostViewAuraTest, DiscardDelegatedFramesWithLocking) {
 TEST_F(RenderWidgetHostViewAuraTest, DiscardDelegatedFramesWithMemoryPressure) {
   view_->InitAsChild(NULL);
 
-  size_t max_renderer_frames =
-      RendererFrameManager::GetInstance()->GetMaxNumberOfSavedFrames();
-  ASSERT_LE(2u, max_renderer_frames);
-  size_t renderer_count = max_renderer_frames;
+  // The test logic below relies on having max_renderer_frames > 2.  By default,
+  // this value is calculated from total physical memory and causes the test to
+  // fail when run on hardware with < 256MB of RAM.
+  const size_t kMaxRendererFrames = 5;
+  RendererFrameManager::GetInstance()->set_max_number_of_saved_frames(
+      kMaxRendererFrames);
+
+  size_t renderer_count = kMaxRendererFrames;
   gfx::Rect view_rect(100, 100);
   gfx::Size frame_size = view_rect.size();
   DCHECK_EQ(0u, HostSharedBitmapManager::current()->AllocatedBitmapCount());

content/browser/renderer_host/renderer_frame_manager.h

@@ -41,6 +41,9 @@ class CONTENT_EXPORT RendererFrameManager {
   size_t GetMaxNumberOfSavedFrames() const;
 
   // For testing only
+  void set_max_number_of_saved_frames(size_t max_number_of_saved_frames) {
+    max_number_of_saved_frames_ = max_number_of_saved_frames;
+  }
   void set_max_handles(float max_handles) { max_handles_ = max_handles; }
 
  private: