Fix issues related to backend texture/rendertarget creation

Change-Id: I640ea5f316e9e4aba778f450655e74636199e0b1
Reviewed-on: https://skia-review.googlesource.com/76440
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
diff --git a/src/gpu/GrResourceProvider.cpp b/src/gpu/GrResourceProvider.cpp
index dfde098..8b36bad 100644
--- a/src/gpu/GrResourceProvider.cpp
+++ b/src/gpu/GrResourceProvider.cpp
@@ -77,7 +77,7 @@
                                                    SkDestinationSurfaceColorMode mipColorMode) {
     ASSERT_SINGLE_OWNER
 
-    SkASSERT(mipLevelCount > 1);
+    SkASSERT(mipLevelCount > 0);
 
     if (this->isAbandoned()) {
         return nullptr;