printing: Make GetWebContentsToUse() accessible to other classes

Move GetWebContentsToUse() from an anonymous namespace to the printing
namespace so it can be used by other classes.

Bug: b:132802107
Test: Build Chrome
Change-Id: I145d5f5a1c6317965828744925a875d27cdff034
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1756714
Commit-Queue: Jesse Schettler <jschettler@chromium.org>
Auto-Submit: Jesse Schettler <jschettler@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#687431}

diff --git a/chrome/browser/printing/print_view_manager_common.h b/chrome/browser/printing/print_view_manager_common.h
index 16b4373..b3c34616 100644
--- a/chrome/browser/printing/print_view_manager_common.h
+++ b/chrome/browser/printing/print_view_manager_common.h

@@ -26,6 +26,10 @@
 // frame (this makes print selection work for multiple frames).
 content::RenderFrameHost* GetFrameToPrint(content::WebContents* contents);
 
+// If we have a single full-page embedded mime handler view guest, print the
+// guest's WebContents instead.
+content::WebContents* GetWebContentsToUse(content::WebContents* contents);
+
 }  // namespace printing
 
 #endif  // CHROME_BROWSER_PRINTING_PRINT_VIEW_MANAGER_COMMON_H_