Simulate low memory warning on devices

  * Add + (void)simulateLowMemoryWarning in NIDeviceInfo.
  * Simulate low memory warning when tapping on NIOverviewMemoryPageView

src/overview/src/NIDeviceInfo.h

@@ -62,6 +62,12 @@ NSString* NIStringFromBytes(unsigned long long bytes);
  */
 + (unsigned long long)bytesOfTotalMemory;
 
+/**
+ * Simulate low memory warning
+ *
+ * Don't use this in production because it uses private API
+ */
++ (void)simulateLowMemoryWarning;
 
 #pragma mark Disk Space /** @name Disk Space */
 
@@ -120,4 +126,5 @@ NSString* NIStringFromBytes(unsigned long long bytes);
  */
 + (void)endCachedDeviceInfo;
 
+
 @end

src/overview/src/NIDeviceInfo.m

@@ -133,6 +133,24 @@ + (unsigned long long)sVMStats.wire_count)
 }
 
 
+///////////////////////////////////////////////////////////////////////////////////////////////////
++ (void)simulateLowMemoryWarning
+{
+  SEL memoryWarningSel =  NSSelectorFromString(@"_performMemoryWarning");
+  if ([[UIApplication sharedApplication] respondsToSelector:memoryWarningSel]) {
+    NIDINFO(@"Simulate low memory warning");
+    // Supress the warning. -Wundeclared-selector was used while ARC is enabled.
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
+    [[UIApplication sharedApplication] performSelector:memoryWarningSel];
+#pragma clang diagnostic pop
+  } else {
+    // UIApplication no loger responds to _performMemoryWarning
+    exit(1);
+  }
+}
+
+
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 + (unsigned long long)bytesOfFreeDiskSpace {
   if (!sIsCaching && ![self updateFileSystemAttributes]) {

src/overview/src/NIOverviewPageView.m

@@ -265,6 +265,11 @@ - (id)initWithFrame:(CGRect)frame {
     self.pageTitle = NSLocalizedString(@"Memory", @"Overview Page Title: Memory");
 
     self.graphView.dataSource = self;
+
+    UITapGestureRecognizer* tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(didTap:)];
+    // We still want to be able to drag the pages.
+    tap.cancelsTouchesInView = NO;
+    [self addGestureRecognizer:tap];
   }
   return self;
 }
@@ -288,6 +293,13 @@ - (void)update {
 }
 
 
+///////////////////////////////////////////////////////////////////////////////////////////////////
+- (void)didTap:(UIGestureRecognizer *)gesture {
+  // Simulate low memory warning while tapping on NIOverviewMemoryPageView
+  [NIDeviceInfo simulateLowMemoryWarning];
+}
+
+
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 #pragma mark -