Add DCHECK in InlineStyleOverrideScope

This is a temporary step to hopefully get more insights into what caused
the crashes.

Bug: 1330656
Change-Id: I3648f7ec58e91fe877c02a55762cb1b33e613b6f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3810483
Auto-Submit: Changhao Han <changhaohan@chromium.org>
Reviewed-by: Alex Rudenko <alexrudenko@chromium.org>
Commit-Queue: Alex Rudenko <alexrudenko@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1032463}

third_party/blink/renderer/core/inspector/inspector_css_agent.h

@@ -89,8 +89,10 @@ class CORE_EXPORT InspectorCSSAgent final
     STACK_ALLOCATED();
 
    public:
-    explicit InlineStyleOverrideScope(ExecutionContext* context)
-        : content_security_policy_(context->GetContentSecurityPolicy()) {
+    explicit InlineStyleOverrideScope(ExecutionContext* context) {
+      DCHECK(context);
+      content_security_policy_ = context->GetContentSecurityPolicy();
+      DCHECK(content_security_policy_);
       content_security_policy_->SetOverrideAllowInlineStyle(true);
     }