Use execute instead of async enqueue OkHttp API on O.

Works around a ClassCastException in OkHttp on O due to a framework bug.

Fixes #2355

integration/okhttp3/src/main/java/com/bumptech/glide/integration/okhttp3/OkHttpStreamFetcher.java

@@ -1,5 +1,6 @@
 package com.bumptech.glide.integration.okhttp3;
 
+import android.os.Build;
 import android.support.annotation.NonNull;
 import android.util.Log;
 import com.bumptech.glide.Priority;
@@ -20,13 +21,15 @@
 /**
  * Fetches an {@link InputStream} using the okhttp library.
  */
-public class OkHttpStreamFetcher implements DataFetcher<InputStream> {
+public class OkHttpStreamFetcher implements DataFetcher<InputStream>,
+ okhttp3.Callback {
   private static final String TAG = "OkHttpFetcher";
   private final Call.Factory client;
   private final GlideUrl url;
   @Synthetic InputStream stream;
   @Synthetic ResponseBody responseBody;
   private volatile Call call;
+  private DataCallback<? super InputStream> callback;
 
   public OkHttpStreamFetcher(Call.Factory client, GlideUrl url) {
     this.client = client;
@@ -41,29 +44,45 @@ public void loadData(Priority priority, final DataCallback<? super InputStream>
       requestBuilder.addHeader(key, headerEntry.getValue());
     }
     Request request = requestBuilder.build();
+    this.callback = callback;
 
     call = client.newCall(request);
-    call.enqueue(new okhttp3.Callback() {
-      @Override
-      public void onFailure(Call call, IOException e) {
-        if (Log.isLoggable(TAG, Log.DEBUG)) {
-          Log.d(TAG, "OkHttp failed to obtain result", e);
-        }
-        callback.onLoadFailed(e);
+    if (Build.VERSION.SDK_INT != Build.VERSION_CODES.O) {
+      call.enqueue(this);
+    } else {
+      try {
+        // Calling execute instead of enqueue is a workaround for #2355, where okhttp throws a
+        // ClassCastException on O.
+        onResponse(call, call.execute());
+      } catch (IOException e) {
+        onFailure(call, e);
+      } catch (ClassCastException e) {
+        // It's not clear that this catch is necessary, the error may only occur even on O if
+        // enqueue is used.
+        onFailure(call, new IOException("Workaround for framework bug on O", e));
       }
+    }
+  }
 
-      @Override
-      public void onResponse(Call call, Response response) throws IOException {
-        responseBody = response.body();
-        if (response.isSuccessful()) {
-          long contentLength = responseBody.contentLength();
-          stream = ContentLengthInputStream.obtain(responseBody.byteStream(), contentLength);
-          callback.onDataReady(stream);
-        } else {
-          callback.onLoadFailed(new HttpException(response.message(), response.code()));
-        }
-      }
-    });
+  @Override
+  public void onFailure(Call call, IOException e) {
+    if (Log.isLoggable(TAG, Log.DEBUG)) {
+      Log.d(TAG, "OkHttp failed to obtain result", e);
+    }
+
+    callback.onLoadFailed(e);
+  }
+
+  @Override
+  public void onResponse(Call call, Response response) throws IOException {
+    responseBody = response.body();
+    if (response.isSuccessful()) {
+      long contentLength = responseBody.contentLength();
+      stream = ContentLengthInputStream.obtain(responseBody.byteStream(), contentLength);
+      callback.onDataReady(stream);
+    } else {
+      callback.onLoadFailed(new HttpException(response.message(), response.code()));
+    }
   }
 
   @Override
@@ -78,6 +97,7 @@ public void cleanup() {
     if (responseBody != null) {
       responseBody.close();
     }
+    callback = null;
   }
 
   @Override