Revert of Enable iPad Tab Switcher by default on iOS.

ios/chrome/browser/snapshots/snapshot_cache_unittest.mm

Index: ios/chrome/browser/snapshots/snapshot_cache_unittest.mm
diff --git a/ios/chrome/browser/snapshots/snapshot_cache_unittest.mm b/ios/chrome/browser/snapshots/snapshot_cache_unittest.mm
index 46e78607eb7c12a72e64d3803b5bf5f827779037..ef3145d505995afe4aa74d6ca81610742849d458 100644
--- a/ios/chrome/browser/snapshots/snapshot_cache_unittest.mm
+++ b/ios/chrome/browser/snapshots/snapshot_cache_unittest.mm
@@ -9,13 +9,15 @@
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/format_macros.h"
+#include "base/ios/ios_util.h"
 #include "base/location.h"
 #include "base/mac/bind_objc_block.h"
 #include "base/mac/scoped_nsautorelease_pool.h"
 #include "base/run_loop.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/time/time.h"
-#import "ios/chrome/browser/snapshots/snapshot_cache_internal.h"
+#include "ios/chrome/browser/experimental_flags.h"
+#include "ios/chrome/browser/ui/ui_util.h"
 #include "ios/web/public/test/test_web_thread_bundle.h"
 #include "ios/web/public/web_thread.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -25,6 +27,12 @@
 static const NSUInteger kSessionCount = 10;
 static const NSUInteger kSnapshotPixelSize = 8;
 
+// Promote some implementation methods to public.
+@interface SnapshotCache (Testing)
++ (base::FilePath)imagePathForSessionID:(NSString*)sessionID;
++ (base::FilePath)greyImagePathForSessionID:(NSString*)sessionID;
+- (void)handleLowMemory;
+@end
 
 namespace {
 
@@ -196,13 +204,6 @@
     return reinterpret_cast<const char*>(CFDataGetBytePtr(data));
   }
 
-  void TriggerMemoryWarning() {
-    // _performMemoryWarning is a private API and musn't be compiled into
-    // official builds.
-    [[UIApplication sharedApplication]
-        performSelector:@selector(_performMemoryWarning)];
-  }
-
   web::TestWebThreadBundle thread_bundle_;
   base::scoped_nsobject<SnapshotCache> snapshotCache_;
   base::scoped_nsobject<NSMutableArray> testSessions_;
@@ -213,13 +214,16 @@
 // As the snapshots are kept in memory, the same pointer can be retrieved.
 // This test also checks that images are correctly removed from the disk.
 TEST_F(SnapshotCacheTest, Cache) {
-  SnapshotCache* cache = GetSnapshotCache();
-
-  if (![cache inMemoryCacheIsEnabled])
+  // Don't run on tablets because color snapshots are not cached so this test
+  // can't compare the UIImage pointers directly.
+  if (IsIPadIdiom() && !experimental_flags::IsTabSwitcherEnabled()) {
     return;
+  }
+
+  SnapshotCache* cache = GetSnapshotCache();
 
   NSUInteger expectedCacheSize = kSessionCount;
-  if ([cache usesLRUCache])
+  if (experimental_flags::IsLRUSnapshotCacheEnabled())
     expectedCacheSize = MIN(kSessionCount, [cache lruCacheMaxSize]);
 
   // Put all images in the cache.
@@ -343,8 +347,16 @@
 }
 
 // Loads the color images into the cache, and pins two of them.  Ensures that
-// only the two pinned IDs remain in memory after a memory warning.
-TEST_F(SnapshotCacheTest, HandleMemoryWarning) {
+// only the two pinned IDs remain in memory after a call to -handleLowMemory.
+TEST_F(SnapshotCacheTest, HandleLowMemory) {
+// TODO(droger): This test fails on iPad iOS8 device: http://crbug.com/455209
+#if !TARGET_IPHONE_SIMULATOR
+  if (IsIPadIdiom() && base::ios::IsRunningOnIOS8OrLater()) {
+    LOG(WARNING) << "Test disabled on iPad iOS8 device.";
+    return;
+  }
+#endif
+
   LoadAllColorImagesIntoCache(true);
 
   SnapshotCache* cache = GetSnapshotCache();
@@ -356,10 +368,15 @@
   [set addObject:secondPinnedID];
   cache.pinnedIDs = set;
 
-  TriggerMemoryWarning();
-
-  EXPECT_EQ(YES, [cache hasImageInMemory:firstPinnedID]);
-  EXPECT_EQ(YES, [cache hasImageInMemory:secondPinnedID]);
+  if (!IsIPadIdiom() || experimental_flags::IsTabSwitcherEnabled())
+    [cache handleLowMemory];
+
+  BOOL expectedValue = YES;
+  if (IsIPadIdiom() && !experimental_flags::IsTabSwitcherEnabled())
+    expectedValue = NO;
+
+  EXPECT_EQ(expectedValue, [cache hasImageInMemory:firstPinnedID]);
+  EXPECT_EQ(expectedValue, [cache hasImageInMemory:secondPinnedID]);
 
   NSString* notPinnedID = [testSessions_ objectAtIndex:2];
   EXPECT_FALSE([cache hasImageInMemory:notPinnedID]);
@@ -406,7 +423,8 @@
   // Remove color images from in-memory cache.
   SnapshotCache* cache = GetSnapshotCache();
 
-  TriggerMemoryWarning();
+  if (!IsIPadIdiom() || experimental_flags::IsTabSwitcherEnabled())
+    [cache handleLowMemory];
 
   // Request the creation of a grey image cache for all images.
   [cache createGreyCache:testSessions_];
@@ -447,7 +465,8 @@
   LoadColorImagesIntoCache(kNumImages, true);
   // Make sure the color images are only on disk, to ensure the background
   // thread is slow enough to queue up the requests.
-  TriggerMemoryWarning();
+  if (!IsIPadIdiom() || experimental_flags::IsTabSwitcherEnabled())
+    [cache handleLowMemory];
 
   // Enable the grey image cache.
   [cache createGreyCache:sessionIDs];
@@ -518,7 +537,8 @@
   NSString* const kSession = @"foo";
   [cache setImage:image withSessionID:kSession];
   FlushRunLoops();  // ensure the file is written to disk.
-  TriggerMemoryWarning();
+  if (!IsIPadIdiom() || experimental_flags::IsTabSwitcherEnabled())
+    [cache handleLowMemory];
 
   // Retrive the image and have the callback verify the size and scale.
   __block BOOL callbackComplete = NO;
@@ -554,7 +574,8 @@
   NSString* const kSession = @"foo";
   [cache setImage:image withSessionID:kSession];
   FlushRunLoops();  // ensure the file is written to disk.
-  TriggerMemoryWarning();
+  if (!IsIPadIdiom() || experimental_flags::IsTabSwitcherEnabled())
+    [cache handleLowMemory];
 
   // Verify the file was writted with @2x in the file name.
   base::FilePath retinaFile = [SnapshotCache imagePathForSessionID:kSession];