Add flag to force purge resources from cache as soon as possible.

Bug: skia:
Change-Id: Ibd636b9e1bf932033c3161c862523f841cb85e79
Reviewed-on: https://skia-review.googlesource.com/c/171005
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
diff --git a/src/gpu/mtl/GrMtlGpu.h b/src/gpu/mtl/GrMtlGpu.h
index 28036bf..a727784 100644
--- a/src/gpu/mtl/GrMtlGpu.h
+++ b/src/gpu/mtl/GrMtlGpu.h
@@ -132,7 +132,8 @@
     sk_sp<GrTexture> onCreateTexture(const GrSurfaceDesc& desc, SkBudgeted budgeted,
                                      const GrMipLevel texels[], int mipLevelCount) override;
 
-    sk_sp<GrTexture> onWrapBackendTexture(const GrBackendTexture&, GrWrapOwnership) override;
+    sk_sp<GrTexture> onWrapBackendTexture(const GrBackendTexture&, GrWrapOwnership,
+                                          bool purgeImmediately) override;
 
     sk_sp<GrTexture> onWrapRenderableBackendTexture(const GrBackendTexture&,
                                                     int sampleCnt,