Android: Don't evict thumbnails for last visible tab on stop

chrome/browser/android/thumbnail/thumbnail_cache.cc

Index: chrome/browser/android/thumbnail/thumbnail_cache.cc
diff --git a/chrome/browser/android/thumbnail/thumbnail_cache.cc b/chrome/browser/android/thumbnail/thumbnail_cache.cc
index 307bbe382983e3f57b8e360b8947001577c54a96..f39525cd3bc10d7d416e8ff956cc8fab373440ba 100644
--- a/chrome/browser/android/thumbnail/thumbnail_cache.cc
+++ b/chrome/browser/android/thumbnail/thumbnail_cache.cc
@@ -8,6 +8,7 @@
 #include <cmath>
 #include <utility>
 
+#include "base/android/application_status_listener.h"
 #include "base/android/path_utils.h"
 #include "base/big_endian.h"
 #include "base/files/file.h"
@@ -131,6 +132,8 @@ ThumbnailCache::ThumbnailCache(size_t default_cache_size,
       ui_resource_provider_(NULL),
       weak_factory_(this) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  memory_pressure_.reset(new base::MemoryPressureListener(
+      base::Bind(&ThumbnailCache::OnMemoryPressure, base::Unretained(this))));
 }
 
 ThumbnailCache::~ThumbnailCache() {
@@ -445,8 +448,23 @@ void ThumbnailCache::RemoveFromReadQueue(TabId tab_id) {
 }
 
 void ThumbnailCache::OnUIResourcesWereEvicted() {
-  cache_.Clear();
-  approximation_cache_.Clear();
+  if (visible_ids_.empty()) {
+    cache_.Clear();
+    approximation_cache_.Clear();
+  } else {
+    TabId last_tab = visible_ids_.front();
+    std::unique_ptr<Thumbnail> thumbnail = cache_.Remove(last_tab);
+    cache_.Clear();
+    std::unique_ptr<Thumbnail> approximation =
+        approximation_cache_.Remove(last_tab);
+    approximation_cache_.Clear();
+
+    // Keep the thumbnail for app resume if it wasn't uploaded yet.
+    if (thumbnail.get() && !thumbnail->ui_resource_id())
+      cache_.Put(last_tab, std::move(thumbnail));
+    if (approximation.get() && !approximation->ui_resource_id())
+      approximation_cache_.Put(last_tab, std::move(approximation));
+  }
 }
 
 void ThumbnailCache::InvalidateCachedThumbnail(Thumbnail* thumbnail) {
@@ -613,7 +631,12 @@ void ThumbnailCache::PostCompressionTask(
     if (thumbnail->time_stamp() != time_stamp)
       return;
     thumbnail->SetCompressedBitmap(compressed_data, content_size);
-    thumbnail->CreateUIResource();
+    // Don't upload the texture if we are being paused/stopped because
+    // the context will go away anyways.
+    if (base::android::ApplicationStatusListener::GetState() ==
+        base::android::APPLICATION_STATE_HAS_RUNNING_ACTIVITIES) {
+      thumbnail->CreateUIResource();
+    }
   }
   WriteThumbnailIfNecessary(tab_id, std::move(compressed_data), scale,
                             content_size);
@@ -909,3 +932,11 @@ std::pair<SkBitmap, float> ThumbnailCache::CreateApproximation(
 
   return std::make_pair(dst_bitmap, new_scale * scale);
 }
+
+void ThumbnailCache::OnMemoryPressure(
+    base::MemoryPressureListener::MemoryPressureLevel level) {
+  if (level == base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL) {
+    cache_.Clear();
+    approximation_cache_.Clear();
+  }
+}