Restore getDevice_just_for_deprecated_compatibility_testing

Change-Id: I98e73a5f72ef8c8efb1a4f382a5359d21bb5edc8
Reviewed-on: https://skia-review.googlesource.com/6325
Reviewed-by: Ravi Mistry <rmistry@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>

include/core/SkCanvas.h

@@ -166,6 +166,10 @@ protected:  // Can we make this private?
 #endif
     SkBaseDevice* getDevice() const;
 public:
+    // Still used internally
+    SkBaseDevice* getDevice_just_for_deprecated_compatibility_testing() const {
+        return this->getDevice();
+    }
 
     /**
      *  saveLayer() can create another device (which is later drawn onto

include/gpu/GrContext.h

@@ -364,7 +364,9 @@ public:
     /** Enumerates all cached GPU resources and dumps their memory to traceMemoryDump. */
     void dumpMemoryStatistics(SkTraceMemoryDump* traceMemoryDump) const;
 
-    /** Get pointer to atlas texture for given mask format */
+    /** Get pointer to atlas texture for given mask format. Note that this wraps an
+        actively mutating texture in an SkImage. This could yield unexpected results
+        if it gets cached or used more generally. */
     sk_sp<SkImage> getFontAtlasImage(GrMaskFormat format);
 
     GrAuditTrail* getAuditTrail() { return &fAuditTrail; }