Fix save/restore while in smask mode

The rendering bug with issue17779.pdf is due to the fact that we call save on the suspended ctx
but not on the the current ctx. So each time we've something like save/transform/restore then
the transform not "removed" when restoring.
So this patch just apply the save/restore operations to ctx which are mirrored on the suspended one.

Author: calixteman

src/display/canvas.js

@@ -1545,39 +1545,35 @@ class CanvasGraphics {
       // Copy the temporary canvas state to the main(suspended) canvas to keep
       // it in sync.
       copyCtxState(this.ctx, this.suspendedCtx);
-      // Don't bother calling save on the temporary canvas since state is not
-      // saved there.
-      this.suspendedCtx.save();
-    } else {
-      this.ctx.save();
     }
+    this.ctx.save();
     const old = this.current;
     this.stateStack.push(old);
     this.current = old.clone();
   }
 
   restore() {
-    if (this.stateStack.length === 0 && this.inSMaskMode) {
-      this.endSMaskMode();
-    }
-    if (this.stateStack.length !== 0) {
-      this.current = this.stateStack.pop();
+    if (this.stateStack.length === 0) {
       if (this.inSMaskMode) {
-        // Graphics state is stored on the main(suspended) canvas. Restore its
-        // state then copy it over to the temporary canvas.
-        this.suspendedCtx.restore();
-        copyCtxState(this.suspendedCtx, this.ctx);
-      } else {
-        this.ctx.restore();
+        this.endSMaskMode();
       }
-      this.checkSMaskState();
-
-      // Ensure that the clipping path is reset (fixes issue6413.pdf).
-      this.pendingClip = null;
+      return;
+    }
 
-      this._cachedScaleForStroking[0] = -1;
-      this._cachedGetSinglePixelWidth = null;
+    this.current = this.stateStack.pop();
+    this.ctx.restore();
+    if (this.inSMaskMode) {
+      // Graphics state is stored on the main(suspended) canvas. Restore its
+      // state then copy it over to the temporary canvas.
+      copyCtxState(this.suspendedCtx, this.ctx);
     }
+    this.checkSMaskState();
+
+    // Ensure that the clipping path is reset (fixes issue6413.pdf).
+    this.pendingClip = null;
+
+    this._cachedScaleForStroking[0] = -1;
+    this._cachedGetSinglePixelWidth = null;
   }
 
   transform(a, b, c, d, e, f) {