Bug 1554985 - Dump the render root boundary information when dumping WR scroll data. r=jrmuizel

Depends on D36385

Differential Revision: https://phabricator.services.mozilla.com/D36386

--HG--
extra : moz-landing-system : lando

gfx/layers/wr/RenderRootBoundary.h

@@ -7,6 +7,9 @@
 
 #include "mozilla/webrender/WebRenderTypes.h"
 
+#include <string>
+#include <sstream>
+
 namespace mozilla {
 namespace layers {
 
@@ -74,6 +77,12 @@ class RenderRootBoundary {
   // constructor for IPC
   RenderRootBoundary() = default;
 
+  std::string ToString() const {
+    std::stringstream str;
+    str << "childType=" << (int)mChildType << "; id=" << mId;
+    return str.str();
+  }
+
  private:
   wr::RenderRoot mChildType;
   // The id is what distinguishes different transition points within a display

gfx/layers/wr/WebRenderScrollData.cpp

@@ -131,6 +131,14 @@ void WebRenderLayerScrollData::Dump(const WebRenderScrollData& aOwner) const {
   if (mReferentId) {
     printf_stderr("  ref layers id: 0x%" PRIx64 "\n", uint64_t(*mReferentId));
   }
+  if (mBoundaryRoot) {
+    printf_stderr("  boundary root for: %s\n",
+                  mBoundaryRoot->ToString().c_str());
+  }
+  if (mReferentRenderRoot) {
+    printf_stderr("  ref renderroot: %s\n",
+                  mReferentRenderRoot->ToString().c_str());
+  }
   printf_stderr("  scrollbar type: %d animation: %" PRIx64 "\n",
                 (int)mScrollbarData.mScrollbarLayerType,
                 mScrollbarAnimationId.valueOr(0));