Cherry pick: Cleanup comments, unit tests and unnecessary early out.

Clean cherry-pick of chromium:

https://crrev.com/947fb1c405943173d09e721efcde628dee896e36

BUG: 17369933
Original description:
Cleanup comments, unit tests and unnecessary early out.

Review URL: https://codereview.chromium.org/545663002
Change-Id: Ia3050dfe65b406b2677f9e10de43ac6665cf953d
Cr-Commit-Position: refs/heads/master@{#294206}
diff --git a/android_webview/browser/browser_view_renderer.cc b/android_webview/browser/browser_view_renderer.cc
index c29ccee..734fa23 100644
--- a/android_webview/browser/browser_view_renderer.cc
+++ b/android_webview/browser/browser_view_renderer.cc
@@ -136,8 +136,7 @@
   // policy should have already been updated.
 }
 
-// This function updates the cached memory policy in shared renderer state, as
-// well as the tile resource allocation in GlobalTileManager.
+// This function updates the resource allocation in GlobalTileManager.
 void BrowserViewRenderer::TrimMemory(const int level, const bool visible) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   // Constants from Android ComponentCallbacks2.
@@ -202,8 +201,6 @@
 
 void BrowserViewRenderer::SetNumTiles(size_t num_tiles,
                                       bool effective_immediately) {
-  if (num_tiles == num_tiles_)
-    return;
   num_tiles_ = num_tiles;
 
   memory_policy_.num_resources_limit = num_tiles_;
diff --git a/android_webview/browser/global_tile_manager.h b/android_webview/browser/global_tile_manager.h
index 3473c20..a4b976b 100644
--- a/android_webview/browser/global_tile_manager.h
+++ b/android_webview/browser/global_tile_manager.h
@@ -31,7 +31,7 @@
 
   void SetTileLimit(size_t num_tiles_limit);
 
-  // Requests the |num_of_tiles| from the available global pool. Calls
+  // Requests the |new_num_of_tiles| from the available global pool. Calls
   // GlobalTileManagerClient.SetNumTiles after the manager determines how many
   // tiles are available for the client. If the number of tiles left is not
   // enough to satisfy the request, the manager will evict tiles allocated to
diff --git a/android_webview/browser/global_tile_manager_unittest.cc b/android_webview/browser/global_tile_manager_unittest.cc
index 9f09084..bd96889 100644
--- a/android_webview/browser/global_tile_manager_unittest.cc
+++ b/android_webview/browser/global_tile_manager_unittest.cc
@@ -90,6 +90,8 @@
     index[i] = i;
   }
 
+  // Fix the seed so that tests are reproducible.
+  std::srand(1);
   // Simulate a random request order of clients.
   std::random_shuffle(&index[0], &index[99]);