For #2392 - Centers private browsing icon

app/src/main/java/org/mozilla/fenix/home/sessioncontrol/viewholders/onboarding/OnboardingPrivateBrowsingViewHolder.kt

@@ -4,6 +4,8 @@
 
 package org.mozilla.fenix.home.sessioncontrol.viewholders.onboarding
 
+import android.graphics.Canvas
+import android.graphics.Paint
 import android.text.SpannableString
 import android.text.Spanned
 import android.text.style.ImageSpan
@@ -12,10 +14,33 @@ import androidx.recyclerview.widget.RecyclerView
 import kotlinx.android.synthetic.main.onboarding_private_browsing.view.*
 import org.mozilla.fenix.R
 
+
+
 class OnboardingPrivateBrowsingViewHolder(view: View) : RecyclerView.ViewHolder(view) {
 
     init {
-        val icon = ImageSpan(view.context, R.drawable.ic_private_browsing)
+        val icon = object : ImageSpan(view.context, R.drawable.ic_private_browsing) {
+            override fun draw(
+                canvas: Canvas,
+                text: CharSequence?,
+                start: Int,
+                end: Int,
+                x: Float,
+                top: Int,
+                y: Int,
+                bottom: Int,
+                paint: Paint
+            ) {
+                canvas.save()
+                val fmPaint = paint.fontMetricsInt
+                val fontHeight = fmPaint.descent - fmPaint.ascent
+                val centerY = y + fmPaint.descent - fontHeight / 2
+                val transY = (centerY - (drawable.bounds.bottom - drawable.bounds.top) / 2).toFloat()
+                canvas.translate(x, transY)
+                drawable.draw(canvas)
+                canvas.restore()
+            }
+        }
         val text = SpannableString(view.context.getString(R.string.onboarding_private_browsing_description))
 
         val spanStartIndex = text.indexOf(IMAGE_PLACEHOLDER)