Source

File: wp-admin/includes/dashboard.php

function wp_dashboard_quick_press( $error_msg = false ) {
	global $post_ID;

	if ( ! current_user_can( 'edit_posts' ) ) {
		return;
	}

	/* Check if a new auto-draft (= no new post_ID) is needed or if the old can be used */
	$last_post_id = (int) get_user_option( 'dashboard_quick_press_last_post_id' ); // Get the last post_ID.
	if ( $last_post_id ) {
		$post = get_post( $last_post_id );
		if ( empty( $post ) || 'auto-draft' !== $post->post_status ) { // auto-draft doesn't exist anymore.
			$post = get_default_post_to_edit( 'post', true );
			update_user_option( get_current_user_id(), 'dashboard_quick_press_last_post_id', (int) $post->ID ); // Save post_ID.
		} else {
			$post->post_title = ''; // Remove the auto draft title.
		}
	} else {
		$post    = get_default_post_to_edit( 'post', true );
		$user_id = get_current_user_id();
		// Don't create an option if this is a super admin who does not belong to this site.
		if ( in_array( get_current_blog_id(), array_keys( get_blogs_of_user( $user_id ) ), true ) ) {
			update_user_option( $user_id, 'dashboard_quick_press_last_post_id', (int) $post->ID ); // Save post_ID.
		}
	}

	$post_ID = (int) $post->ID;
	?>

	<form name="post" action="<?php echo esc_url( admin_url( 'post.php' ) ); ?>" method="post" id="quick-press" class="initial-form hide-if-no-js">

		<?php if ( $error_msg ) : ?>
		<div class="error"><?php echo $error_msg; ?></div>
		<?php endif; ?>

		<div class="input-text-wrap" id="title-wrap">
			<label for="title">
				<?php
				/** This filter is documented in wp-admin/edit-form-advanced.php */
				echo apply_filters( 'enter_title_here', __( 'Title' ), $post );
				?>
			</label>
			<input type="text" name="post_title" id="title" autocomplete="off" />
		</div>

		<div class="textarea-wrap" id="description-wrap">
			<label for="content"><?php _e( 'Content' ); ?></label>
			<textarea name="content" id="content" placeholder="<?php esc_attr_e( 'What&#8217;s on your mind?' ); ?>" class="mceEditor" rows="3" cols="15" autocomplete="off"></textarea>
		</div>

		<p class="submit">
			<input type="hidden" name="action" id="quickpost-action" value="post-quickdraft-save" />
			<input type="hidden" name="post_ID" value="<?php echo $post_ID; ?>" />
			<input type="hidden" name="post_type" value="post" />
			<?php wp_nonce_field( 'add-post' ); ?>
			<?php submit_button( __( 'Save Draft' ), 'primary', 'save', false, array( 'id' => 'save-post' ) ); ?>
			<br class="clear" />
		</p>

	</form>
	<?php
	wp_dashboard_recent_drafts();
}