API parameter consistency

Ensure consistent parameter handling across API methods by using appropriate defaults, proper type conversion, validation with meaningful constants, and cross-platform behavior consistency.

Key practices:

• Use default parameters to simplify common use cases: void SetBounds(const gfx::Rect& bounds, bool animate = false)
• Leverage built-in type converters instead of manual string conversion: dict.Get("frameOrigin", &frame_origin_url) where frame_origin_url is a GURL
• Use symbolic constants with documentation for validation: constexpr int kMinSizeReqdBySpec = 100; // Per Web API spec
• Apply consistent validation patterns: width = std::max(kMinSizeReqdBySpec, inner_width)
• Provide consistent fallback values: Use “unknown” instead of empty strings for enum-like values
• Use std::move() for optional parameters: SetUserAgent(user_agent, std::move(ua_metadata))
• Maintain cross-platform consistency: Either implement identical behavior across platforms or explicitly gate platform-specific APIs
• Avoid hardcoded values: Make configurable what users might want to customize (e.g., animation duration)

This approach reduces API complexity, improves type safety, and ensures predictable behavior across different platforms and use cases.