Sprinkle null-checks in an attempt to "fix" the orange so I can get answers.

layout/base/nsPresShell.cpp

@@ -4681,7 +4681,7 @@ PresShell::StyleSheetAdded(nsIDocument *aDocument,
   aStyleSheet->GetApplicable(applicable);
 
   if (applicable && aStyleSheet->HasRules()) {
-    if (mDidInitialReflow) {
+    if (mDidInitialReflow && mDocument && mDocument->GetDocumentURI()) {
       nsCAutoString uri;
       mDocument->GetDocumentURI()->GetSpec(uri);
       printf("Sheet added after StartLayout on %s\n", uri.get());
@@ -4700,7 +4700,7 @@ PresShell::StyleSheetRemoved(nsIDocument *aDocument,
   PRBool applicable;
   aStyleSheet->GetApplicable(applicable);
   if (applicable && aStyleSheet->HasRules()) {
-    if (mDidInitialReflow) {
+    if (mDidInitialReflow && mDocument && mDocument->GetDocumentURI()) {
       nsCAutoString uri;
       mDocument->GetDocumentURI()->GetSpec(uri);
       printf("Sheet removed after StartLayout on %s\n", uri.get());
@@ -4715,7 +4715,7 @@ PresShell::StyleSheetApplicableStateChanged(nsIDocument *aDocument,
                                             PRBool aApplicable)
 {
   if (aStyleSheet->HasRules()) {
-    if (mDidInitialReflow) {
+    if (mDidInitialReflow && mDocument && mDocument->GetDocumentURI()) {
       nsCAutoString uri;
       mDocument->GetDocumentURI()->GetSpec(uri);
       printf("Sheet state toggled after StartLayout on %s\n", uri.get());

layout/generic/nsHTMLFrame.cpp

@@ -612,11 +612,13 @@ CanvasFrame::Reflow(nsPresContext*          aPresContext,
     FinishAndStoreOverflow(&aDesiredSize);
   }
 
+  if (mContent && mContent->GetOwnerDoc() && mContent->GetOwnerDoc()->GetDocumentURI()) {
     nsCAutoString uri;
-  mContent->GetDocument()->GetDocumentURI()->GetSpec(uri);
+    mContent->GetOwnerDoc()->GetDocumentURI()->GetSpec(uri);
     printf("Finished canvas reflow for %s:\n"
            "Height: %d, overflow height: %d\n",
            uri.get(), aDesiredSize.height, aDesiredSize.mOverflowArea.height);
+  }
 
   NS_FRAME_TRACE_REFLOW_OUT("CanvasFrame::Reflow", aStatus);
   NS_FRAME_SET_TRUNCATION(aStatus, aReflowState, aDesiredSize);