Add list of dependents to GrOpList class

This is pulled out of: https://skia-review.googlesource.com/c/skia/+/143113 (Reduce arbitrary opList splitting when sorting (take 3)) and is necessary for incremental tological sorting of opLists.

Change-Id: I080cee2c54f5a61dceea67037242f6c6b3e01b8d
Reviewed-on: https://skia-review.googlesource.com/145641
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>

include/private/GrOpList.h

@@ -117,6 +117,9 @@ class GrOpList : public SkRefCnt {
     friend class GrDrawingManager; // for resetFlag, TopoSortTraits & gatherProxyIntervals
 
     void addDependency(GrOpList* dependedOn);
+    void addDependent(GrOpList* dependent);
+    SkDEBUGCODE(bool isDependedent(const GrOpList* dependent) const);
+    SkDEBUGCODE(void validate() const);
 
     // Remove all Ops which reference proxies that have not been instantiated.
     virtual void purgeOpsWithUninstantiatedProxies() = 0;
@@ -177,6 +180,8 @@ class GrOpList : public SkRefCnt {
 
     // 'this' GrOpList relies on the output of the GrOpLists in 'fDependencies'
     SkSTArray<1, GrOpList*, true> fDependencies;
+    // 'this' GrOpList's output is relied on by the GrOpLists in 'fDependents'
+    SkSTArray<1, GrOpList*, true> fDependents;
 
     typedef SkRefCnt INHERITED;
 };

src/gpu/GrOpList.cpp

@@ -97,6 +97,9 @@ void GrOpList::addDependency(GrOpList* dependedOn) {
     }
 
     fDependencies.push_back(dependedOn);
+    dependedOn->addDependent(this);
+
+    SkDEBUGCODE(this->validate());
 }
 
 // Convert from a GrSurface-based dependency to a GrOpList one
@@ -135,6 +138,31 @@ bool GrOpList::dependsOn(const GrOpList* dependedOn) const {
     return false;
 }
 
+
+void GrOpList::addDependent(GrOpList* dependent) {
+    fDependents.push_back(dependent);
+}
+
+#ifdef SK_DEBUG
+bool GrOpList::isDependedent(const GrOpList* dependent) const {
+    for (int i = 0; i < fDependents.count(); ++i) {
+        if (fDependents[i] == dependent) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
+void GrOpList::validate() const {
+    // TODO: check for loops and duplicates
+
+    for (int i = 0; i < fDependencies.count(); ++i) {
+        SkASSERT(fDependencies[i]->isDependedent(this));
+    }
+}
+#endif
+
 bool GrOpList::isInstantiated() const { return fTarget.get()->isInstantiated(); }
 
 bool GrOpList::isFullyInstantiated() const {
@@ -181,6 +209,12 @@ void GrOpList::dump(bool printDependencies) const {
             SkDebugf("%d, ", fDependencies[i]->fUniqueID);
         }
         SkDebugf("\n");
+
+        SkDebugf("(%d) Rely On Me: ", fDependents.count());
+        for (int i = 0; i < fDependents.count(); ++i) {
+            SkDebugf("%d, ", fDependents[i]->fUniqueID);
+        }
+        SkDebugf("\n");
     }
 }
 #endif