Properly recompute SVG font size under zoom

Source/core/rendering/svg/RenderSVGInlineText.cpp

Index: Source/core/rendering/svg/RenderSVGInlineText.cpp
diff --git a/Source/core/rendering/svg/RenderSVGInlineText.cpp b/Source/core/rendering/svg/RenderSVGInlineText.cpp
index ac41b9fddbf2f02a23f58e81fcb9f5a45c442182..a2399292c5a73a112ec8192d2739e8431b3098e0 100644
--- a/Source/core/rendering/svg/RenderSVGInlineText.cpp
+++ b/Source/core/rendering/svg/RenderSVGInlineText.cpp
@@ -220,7 +220,7 @@ void RenderSVGInlineText::computeNewScaledFontForStyle(RenderObject* renderer, c
 
     // Alter font-size to the right on-screen value to avoid scaling the glyphs themselves, except when GeometricPrecision is specified.
     scalingFactor = SVGRenderingContext::calculateScreenFontSizeScalingFactor(renderer);
-    if (scalingFactor == 1 || !scalingFactor) {

[f(malita), 2014/08/27 12:44:31]

Not related to this CL, but do you know why we reset 0.0 -> 1.0? It seems odd
that at the low end of our range, the font snaps back to visible.

[pdr., 2014/08/27 18:09:51]

I agree, this is weird.

I tried converting this to an assert:
    ASSERT(scalingFactor);
    if (style->effectiveZoom() == 1 && scalingFactor == 1)

Unfortunately it looks like scalingFactor will sometimes actually be zero. This
is probably a bug since scalingFactor is effectively the full ctm. This code has
some gross bugs and does not work properly with the compositing update :/

+    if (style->effectiveZoom() == 1 && (scalingFactor == 1 || !scalingFactor)) {
         scalingFactor = 1;
         scaledFont = style->font();
         return;