Fix failing svg canvas test (#1977)
Fix failing svg canvas test (#1977)

Partial fix for #1976. This fixes the broken test by initializing the
svg for blocks when they're created.
twodee/blockly,rachel-fenichel/blockly,google/blockly,nickmain/blockly,twodee/blockly,joshlory/blockly,rachel-fenichel/blockly,joshlory/blockly,nickmain/blockly,trinketapp/blockly,nickmain/blockly,rachel-fenichel/blockly,google/blockly,mark-friedman/blockly,mark-friedman/blockly,twodee/blockly,trinketapp/blockly,google/blockly,twodee/blockly,google/blockly,twodee/blockly,mark-friedman/blockly,rachel-fenichel/blockly,mark-friedman/blockly,picklesrus/blockly,rachel-fenichel/blockly,twodee/blockly,picklesrus/blockly,rachel-fenichel/blockly,mark-friedman/blockly,nickmain/blockly,trinketapp/blockly,google/blockly,rachel-fenichel/blockly,google/blockly,nickmain/blockly,google/blockly,trinketapp/blockly,picklesrus/blockly,mark-friedman/blockly,joshlory/blockly,nickmain/blockly