Bug 1851861: Null-check more calls that attempt to create a DrawTarget. r=gfx-reviewers,lsalzman

Most of our calls that create a DrawTarget are null-checked. This patch
fixes up the few that were not already checked.

Differential Revision: https://phabricator.services.mozilla.com/D187586

gfx/2d/DrawTargetCairo.cpp

@@ -1803,9 +1803,13 @@ RefPtr<DrawTarget> DrawTargetCairo::CreateClippedDrawTarget(
   if (!clipBounds.IsEmpty()) {
     RefPtr<DrawTarget> dt = CreateSimilarDrawTarget(
         IntSize(clipBounds.width, clipBounds.height), aFormat);
-    result = gfx::Factory::CreateOffsetDrawTarget(
-        dt, IntPoint(clipBounds.x, clipBounds.y));
-    result->SetTransform(mTransform);
+    if (dt) {
+      result = gfx::Factory::CreateOffsetDrawTarget(
+          dt, IntPoint(clipBounds.x, clipBounds.y));
+      if (result) {
+        result->SetTransform(mTransform);
+      }
+    }
   } else {
     // Everything is clipped but we still want some kind of surface
     result = CreateSimilarDrawTarget(IntSize(1, 1), aFormat);

gfx/2d/DrawTargetD2D1.cpp

@@ -1230,8 +1230,12 @@ RefPtr<DrawTarget> DrawTargetD2D1::CreateClippedDrawTarget(
   IntRect rect = RoundedOut(ToRect(clipRect));
 
   RefPtr<DrawTarget> dt = CreateSimilarDrawTarget(rect.Size(), aFormat);
-  result = gfx::Factory::CreateOffsetDrawTarget(dt, rect.TopLeft());
-  result->SetTransform(mTransform);
+  if (dt) {
+    result = gfx::Factory::CreateOffsetDrawTarget(dt, rect.TopLeft());
+    if (result) {
+      result->SetTransform(mTransform);
+    }
+  }
   if (!aBounds.IsEmpty()) {
     PopClip();
   }

gfx/webrender_bindings/Moz2DImageRenderer.cpp

@@ -370,22 +370,25 @@ static bool Moz2DRenderCallback(const Range<const uint8_t> aBlob,
     return false;
   }
 
+  // aRenderRect is the part of the blob that we are currently rendering
+  // (for example a tile) in the same coordinate space as aVisibleRect.
+  IntPoint origin = gfx::IntPoint(aRenderRect->min.x, aRenderRect->min.y);
+
+  dt = gfx::Factory::CreateOffsetDrawTarget(dt, origin);
+  if (!dt) {
+    return false;
+  }
+
   // We try hard to not have empty blobs but we can end up with
   // them because of CompositorHitTestInfo and merging.
   size_t footerSize = sizeof(size_t);
   MOZ_RELEASE_ASSERT(aBlob.length() >= footerSize);
   size_t indexOffset = ConvertFromBytes<size_t>(aBlob.end().get() - footerSize);
 
-  // aRenderRect is the part of the blob that we are currently rendering
-  // (for example a tile) in the same coordinate space as aVisibleRect.
-  IntPoint origin = gfx::IntPoint(aRenderRect->min.x, aRenderRect->min.y);
-
   MOZ_RELEASE_ASSERT(indexOffset <= aBlob.length() - footerSize);
   Reader reader(aBlob.begin().get() + indexOffset,
                 aBlob.length() - footerSize - indexOffset);
 
-  dt = gfx::Factory::CreateOffsetDrawTarget(dt, origin);
-
   auto bounds = gfx::IntRect(origin, size);
 
   if (aDirtyRect) {