Make re-scanning of devices much faster by caching content hashcodes.

This CL is took over from issue 1112573005 at patchset 30001 (http://crrev.com/1112573005#ps30001)

BUG=476688
TEST=*ImportController*

Review URL: https://codereview.chromium.org/1126043005

Cr-Commit-Position: refs/heads/master@{#329377}

ui/file_manager/file_manager/background/js/duplicate_finder.js

@@ -20,6 +20,13 @@ importer.DriveDuplicateFinder = function(tracker) {
 
   /** @private {Promise<string>} */
   this.driveIdPromise_ = null;
+
+  /**
+   * An bounded cache of most recently calculated file content hashcodes.
+   * @private {!LRUCache<!Promise<string>>}
+   */
+  this.hashCache_ = new LRUCache(
+      importer.DriveDuplicateFinder.MAX_CACHED_HASHCODES_);
 };
 
 /**
@@ -45,42 +52,57 @@ importer.DriveDuplicateFinder.HASH_EVENT_THRESHOLD_ = 5000;
 /** @private @const {number} */
 importer.DriveDuplicateFinder.SEARCH_EVENT_THRESHOLD_ = 1000;
 
+/** @private @const {number} */
+importer.DriveDuplicateFinder.MAX_CACHED_HASHCODES_ = 10000;
+
 /**
  * Computes the content hash for the given file entry.
  * @param {!FileEntry} entry
+ * @return {!Promise<string>} The computed hash.
  * @private
  */
 importer.DriveDuplicateFinder.prototype.computeHash_ = function(entry) {
-  return new Promise(
-      /** @this {importer.DriveDuplicateFinder} */
-      function(resolve, reject) {
-        var startTime = new Date().getTime();
-        chrome.fileManagerPrivate.computeChecksum(
-            entry.toURL(),
-            /**
-             * @param {string} result The content hash.
-             * @this {importer.DriveDuplicateFinder}
-             */
-            function(result) {
-              var elapsedTime = new Date().getTime() - startTime;
-              // Send the timing to GA only if it is sorta exceptionally long.
-              // A one second, CPU intensive operation, is pretty long.
-              if (elapsedTime >=
-                  importer.DriveDuplicateFinder.HASH_EVENT_THRESHOLD_) {
-                console.info(
-                    'Content hash computation took ' + elapsedTime + ' ms.');
-                this.tracker_.sendTiming(
-                   metrics.Categories.ACQUISITION,
-                   metrics.timing.Variables.COMPUTE_HASH,
-                   elapsedTime);
-              }
-              if (chrome.runtime.lastError) {
-                reject(chrome.runtime.lastError);
-              } else {
-                resolve(result);
-              }
-            }.bind(this));
-      }.bind(this));
+  return importer.createMetadataHashcode(entry).then(function(hashcode) {
+    // Cache key is the concatination of metadata hashcode and URL.
+    var cacheKey = hashcode + '|' + entry.toURL();
+    if (this.hashCache_.hasKey(cacheKey)) {
+      return this.hashCache_.get(cacheKey);
+    }
+
+    var hashPromise = new Promise(
+        /** @this {importer.DriveDuplicateFinder} */
+        function(resolve, reject) {
+          var startTime = new Date().getTime();
+          chrome.fileManagerPrivate.computeChecksum(
+              entry.toURL(),
+              /**
+               * @param {string} result The content hash.
+               * @this {importer.DriveDuplicateFinder}
+               */
+              function(result) {
+                var elapsedTime = new Date().getTime() - startTime;
+                // Send the timing to GA only if it is sorta exceptionally long.
+                // A one second, CPU intensive operation, is pretty long.
+                if (elapsedTime >=
+                    importer.DriveDuplicateFinder.HASH_EVENT_THRESHOLD_) {
+                  console.info(
+                      'Content hash computation took ' + elapsedTime + ' ms.');
+                  this.tracker_.sendTiming(
+                     metrics.Categories.ACQUISITION,
+                     metrics.timing.Variables.COMPUTE_HASH,
+                     elapsedTime);
+                }
+                if (chrome.runtime.lastError) {
+                  reject(chrome.runtime.lastError);
+                } else {
+                  resolve(result);
+                }
+              }.bind(this));
+        }.bind(this));
+
+    this.hashCache_.put(cacheKey, hashPromise);
+    return hashPromise;
+  }.bind(this));
 };
 
 /**
@@ -91,8 +113,9 @@ importer.DriveDuplicateFinder.prototype.computeHash_ = function(entry) {
  * @private
  */
 importer.DriveDuplicateFinder.prototype.findByHash_ = function(hash) {
-  return this.getDriveId_()
-      .then(this.searchFilesByHash_.bind(this, hash));
+  return /** @type {!Promise<Array<string>>} */ (
+      this.getDriveId_()
+          .then(this.searchFilesByHash_.bind(this, hash)));
 };
 
 /**
@@ -119,7 +142,8 @@ importer.DriveDuplicateFinder.prototype.getDriveId_ = function() {
  * A promise-based wrapper for chrome.fileManagerPrivate.searchFilesByHashes.
  * @param {string} hash The content hash to search for.
  * @param {string} volumeId The volume to search.
- * @return <!Promise<Array<string>>> A list of file URLs.
+ * @return {!Promise<Array<string>>} A list of file URLs.
+ * @private
  */
 importer.DriveDuplicateFinder.prototype.searchFilesByHash_ =
     function(hash, volumeId) {

ui/file_manager/file_manager/background/js/duplicate_finder_unittest.html

@@ -13,6 +13,7 @@
   <script src="../../../../../ui/webui/resources/js/load_time_data.js"></script>
 
   <script src="../../common/js/async_util.js"></script>
+  <script src="../../common/js/lru_cache.js"></script>
   <script src="../../common/js/mock_entry.js"></script>
   <script src="../../common/js/test_tracker.js"></script>
   <script src="../../common/js/unittest_util.js"></script>

ui/file_manager/file_manager/background/js/media_scanner.js

@@ -121,7 +121,9 @@ importer.DefaultMediaScanner.prototype.scanDirectory = function(directory) {
       .then(
           /** @this {importer.DefaultMediaScanner} */
           function() {
-            console.info(scan.name + ': Finished.');
+            console.info(
+                scan.name + ': Finished directory scan. Details: ' +
+                JSON.stringify(scan.getStatistics()));
             this.notify_(importer.ScanEvent.FINALIZED, scan);
           }.bind(this));
 
@@ -155,7 +157,9 @@ importer.DefaultMediaScanner.prototype.scanFiles = function(entries) {
       .then(
           /** @this {importer.DefaultMediaScanner} */
           function() {
-            console.info(scan.name + ': Finished.');
+            console.info(
+                scan.name + ': Finished file-selection scan. Details: ' +
+                JSON.stringify(scan.getStatistics()));
             this.notify_(importer.ScanEvent.FINALIZED, scan);
           }.bind(this));
 

ui/file_manager/file_manager/common/js/lru_cache.js

@@ -126,6 +126,15 @@ LRUCache.prototype.peek = function(key) {
   return node.value;
 };
 
+/**
+ * Returns true if the cache contains the key.
+ * @param {string} key
+ * @return {boolean}
+ */
+LRUCache.prototype.hasKey = function(key) {
+  return key in this.nodes_;
+};
+
 /**
  * Saves an item in this cache. The saved item will be the most recently used
  * item and won't be evicted soon. If an item with the same key already exists

ui/file_manager/file_manager/manifest.json

@@ -181,6 +181,7 @@
         "chrome://resources/js/analytics.js",
         "common/js/async_util.js",
         "common/js/file_type.js",
+        "common/js/lru_cache.js",
         "common/js/metrics_base.js",
         "common/js/metrics_events.js",
         "common/js/metrics.js",

ui/file_manager/file_manager_resources.grd

@@ -28,6 +28,7 @@
       <include name="IDR_FILE_MANAGER_METRICS_BASE_JS" file="file_manager/common/js/metrics_base.js" flattenhtml="false" type="BINDATA" />
       <include name="IDR_FILE_MANAGER_METRICS_JS" file="file_manager/common/js/metrics.js" flattenhtml="false" type="BINDATA" />
       <include name="IDR_FILE_MANAGER_METRICS_EVENTS_JS" file="file_manager/common/js/metrics_events.js" flattenhtml="false" type="BINDATA" />
+      <include name="IDR_FILE_MANAGER_LRU_CACHE_JS" file="file_manager/common/js/lru_cache.js" flattenhtml="false" type="BINDATA" />
 
       <!-- Scripts working in background page. -->
       <include name="IDR_FILE_MANAGER_DEVICE_APP_WINDOW_WRAPPER_JS" file="file_manager/background/js/app_window_wrapper.js" flattenhtml="false" type="BINDATA" />