[Files.app] Change sort timing during metadata fetch

chrome/browser/resources/file_manager/foreground/js/metadata/metadata_cache.js

Index: chrome/browser/resources/file_manager/foreground/js/metadata/metadata_cache.js
diff --git a/chrome/browser/resources/file_manager/foreground/js/metadata/metadata_cache.js b/chrome/browser/resources/file_manager/foreground/js/metadata/metadata_cache.js
index 75dabec132323901386012c85aa231ec7e35a55c..8ceeb96be3f4d96c50867c31d3c2a79ff5268f5c 100644
--- a/chrome/browser/resources/file_manager/foreground/js/metadata/metadata_cache.js
+++ b/chrome/browser/resources/file_manager/foreground/js/metadata/metadata_cache.js
@@ -77,6 +77,8 @@ function MetadataCache() {
   this.batchCount_ = 0;
   this.totalCount_ = 0;
 
+  this.currentContentNumber_ = 0;
+
   /**
    * Time of first get query of the current batch. Items updated later than this
    * will not be evicted.
@@ -159,6 +161,27 @@ MetadataCache.prototype.isInitialized = function() {
 };
 
 /**
+ * Sets the number of contents currently shown.
+ * @param {number} number The number of the contents currently shown.
+ **/
+MetadataCache.prototype.setCurrentContentNumber = function(number) {

[mtomasz, 2013/12/24 00:22:10]

Contents is uncountable. Also, Cache shouldn't know about number of items being
shown. How about setCacheSize()?

[yoshiki, 2014/01/08 08:08:31]

Thanks! Done.

+  this.currentContentNumber_ = number;
+
+  if (this.totalCount_ > this.currentEvictionNumber_())
+    this.evict_();
+};
+
+/**
+ * Returns the current threshold to evict caches. When the number of caches
+ * exceeds this, the cache should be evicted.
+ * @return {number} Threshold to evict caches.
+ * @private
+ */
+MetadataCache.prototype.currentEvictionThreshold_ = function() {
+  return this.currentContentNumber_ * 2 + MetadataCache.EVICTION_NUMBER / 2;

[mtomasz, 2013/12/24 00:22:10]

Eviction policy got tricky here. Why this formula? Why do you divide
EVICTION_NUMBER by 2? Can you please add a comment?

[yoshiki, 2014/01/08 08:08:31]

Made the rule and the code simpler.

+};
+
+/**
  * Fetches the metadata, puts it in the cache, and passes to callback.
  * If required metadata is already in the cache, does not fetch it again.
  * @param {string|Entry|Array.<string|Entry>} items The list of entries or
@@ -456,7 +479,7 @@ MetadataCache.prototype.startBatchUpdates = function() {
 MetadataCache.prototype.endBatchUpdates = function() {
   this.batchCount_--;
   if (this.batchCount_ != 0) return;
-  if (this.totalCount_ > MetadataCache.EVICTION_NUMBER)
+  if (this.totalCount_ > this.currentEvictionThreshold_())
     this.evict_();
   for (var index = 0; index < this.observers_.length; index++) {
     var observer = this.observers_[index];
@@ -504,7 +527,7 @@ MetadataCache.prototype.evict_ = function() {
   var toRemove = [];
 
   // We leave only a half of items, so we will not call evict_ soon again.
-  var desiredCount = Math.round(MetadataCache.EVICTION_NUMBER / 2);
+  var desiredCount = Math.round(this.currentEvictionThreshold_() / 2);
   var removeCount = this.totalCount_ - desiredCount;
   for (var url in this.cache_) {
     if (this.cache_.hasOwnProperty(url) &&