Revert "Fix texture barriers on DMSAA"

This reverts commit 1a3f4ab4901c2294d13c785717655ce059eb42fa.

Reason for revert: breaking dmsaa test on intel hd405, https://ci.chromium.org/raw/build/logs.chromium.org/skia/54538c41f1c1b111/+/annotations

Original change's description:
> Fix texture barriers on DMSAA
>
> Bug: skia:11396
> Change-Id: Iad74958c05ed086fe85656b9dc5418d5ab4589e7
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/419838
> Commit-Queue: Greg Daniel <egdaniel@google.com>
> Reviewed-by: Chris Dalton <csmartdalton@google.com>
> Reviewed-by: Brian Salomon <bsalomon@google.com>

TBR=egdaniel@google.com,bsalomon@google.com,csmartdalton@google.com

Change-Id: I8be8107a98584dfb7f831a296078753fecfcebcf
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:11396
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/421056
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
diff --git a/src/gpu/GrDrawingManager.cpp b/src/gpu/GrDrawingManager.cpp
index ab32cd9..3c9b49f 100644
--- a/src/gpu/GrDrawingManager.cpp
+++ b/src/gpu/GrDrawingManager.cpp
@@ -373,14 +373,14 @@
 
 #ifdef SK_DEBUG
     // This block checks for any unnecessary splits in the opsTasks. If two sequential opsTasks
-    // could have merged it means the opsTask was artificially split.
+    // share the same backing GrSurfaceProxy it means the opsTask was artificially split.
     if (!fDAG.empty()) {
         GrOpsTask* prevOpsTask = fDAG[0]->asOpsTask();
         for (int i = 1; i < fDAG.count(); ++i) {
             GrOpsTask* curOpsTask = fDAG[i]->asOpsTask();
 
             if (prevOpsTask && curOpsTask) {
-                SkASSERT(!prevOpsTask->canMerge(curOpsTask));
+                SkASSERT(prevOpsTask->target(0) != curOpsTask->target(0));
             }
 
             prevOpsTask = curOpsTask;