bypass memory cache, cache policy, and normal tile source fetches

@@ -34,6 +34,8 @@
 #import "RMConfiguration.h"
 #import "RMTileSource.h"
 
+#import "RMAbstractWebMapSource.h"
+
 #import "RMTileCacheDownloadOperation.h"
 
 @interface RMTileCache (Configuration)
@@ -326,6 +328,8 @@
     if (self.isBackgroundCaching)
         return;
 
+    NSAssert([tileSource isKindOfClass:[RMAbstractWebMapSource class]], @"only web-based tile sources are supported for downloading");
+
     _activeTileSource = tileSource;
 
     _backgroundFetchQueue = [NSOperationQueue new];

@@ -26,6 +26,8 @@
 // POSSIBILITY OF SUCH DAMAGE.
 
 #import "RMTileCacheDownloadOperation.h"
+#import "RMAbstractWebMapSource.h"
+#import "RMConfiguration.h"
 
 @implementation RMTileCacheDownloadOperation
 {
@@ -39,6 +41,8 @@
     if (!(self = [super init]))
         return nil;
 
+    NSAssert([_source isKindOfClass:[RMAbstractWebMapSource class]], @"only web-based tile sources are supported for downloading");
+
     _tile   = tile;
     _source = source;
     _cache  = cache;
@@ -54,13 +58,27 @@
     if ([self isCancelled])
         return;
 
-    if ( ! [_cache cachedImage:_tile withCacheKey:[_source uniqueTilecacheKey]])
+    if ( ! [_cache cachedImage:_tile withCacheKey:[_source uniqueTilecacheKey] bypassingMemoryCache:YES])
     {
         if ([self isCancelled])
             return;
 
-        if ( ! [_source imageForTile:_tile inCache:_cache])
+        NSURL *tileURL = [(RMAbstractWebMapSource *)_source URLForTile:_tile];
+        NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:tileURL];
+        request.cachePolicy = NSURLRequestReloadIgnoringLocalCacheData;
+        NSError *error = nil;
+        NSData *data = [NSURLConnection sendBrandedSynchronousRequest:request
+                                                    returningResponse:nil
+                                                                error:&error];
+
+        if ( ! data || error != nil)
+        {
             [self cancel];
+        }
+        else
+        {
+            [_cache addDiskCachedImageData:data forTile:_tile withCacheKey:[_source uniqueTilecacheKey]];
+        }
     }
 }