Add camera focus area API.

const char CameraParameters::KEY_SUPPORTED_FLASH_MODES[] = "flash-mode-values";

const char CameraParameters::KEY_FOCUS_MODE[] = "focus-mode";

const char CameraParameters::KEY_SUPPORTED_FOCUS_MODES[] = "focus-mode-values";

const char CameraParameters::KEY_MAX_NUM_FOCUS_AREAS[] = "max-num-focus-areas";

const char CameraParameters::KEY_FOCUS_AREAS[] = "focus-areas";

const char CameraParameters::KEY_FOCAL_LENGTH[] = "focal-length";

const char CameraParameters::KEY_HORIZONTAL_VIEW_ANGLE[] = "horizontal-view-angle";

const char CameraParameters::KEY_VERTICAL_VIEW_ANGLE[] = "vertical-view-angle";

    // Supported focus modes.

    // Example value: "auto,macro,fixed". Read only.

    static const char KEY_SUPPORTED_FOCUS_MODES[];

    // The maximum number of focus areas supported. This is the maximum length

    // of KEY_FOCUS_AREAS.

    // Example value: "0" or "2". Read only.

    static const char KEY_MAX_NUM_FOCUS_AREAS[];

    // Current focus areas.

    //

    // Before accessing this parameter, apps should check

    // KEY_MAX_NUM_FOCUS_AREAS first to know the maximum number of focus areas

    // first. If the value is 0, focus area is not supported.

    //

    // Each focus area is a five-element int array. The first four elements are

    // the rectangle of the area (left, top, right, bottom). The direction is

    // relative to the sensor orientation, that is, what the sensor sees. The

    // direction is not affected by the rotation or mirroring of

    // CAMERA_CMD_SET_DISPLAY_ORIENTATION. Coordinates range from -1000 to 1000.

    // (-1000,-1000) is the upper left point. (1000, 1000) is the lower right

    // point. The length and width of focus areas cannot be 0 or negative.

    //

    // The fifth element is the weight. The weight ranges from 1 to 1000.

    // The sum of the weights of all focus areas must be 1000. Focus areas

    // can partially overlap and the driver will add the weights in the

    // overlap region. But apps should not set two focus areas that have

    // identical coordinates.

    //

    // A special case of single focus area (0,0,0,0,0) means driver to decide

    // the focus area. For example, the driver may use more signals to decide

    // focus areas and change them dynamically. Apps can set (0,0,0,0,0) if they

    // want the driver to decide focus areas.

    //

    // Focus areas are relative to the current field of view (KEY_ZOOM). No

    // matter what the zoom level is, (-1000,-1000) represents the top of the

    // currently visible camera frame. The focus area cannot be set to be

    // outside the current field of view, even when using zoom.

    //

    // Focus area only has effect if the current focus mode is FOCUS_MODE_AUTO,

    // FOCUS_MODE_MACRO, or FOCUS_MODE_CONTINOUS_VIDEO.

    // Example value: "(-10,-10,0,0,300),(0,0,10,10,700)". Read/write.

    static const char KEY_FOCUS_AREAS[];

    // Focal length in millimeter.

    // Example value: "4.31". Read only.

    static const char KEY_FOCAL_LENGTH[];