In Romeo and Juliet who quotes "Thy head is as full of quarrels as an egg is full of meat..."I need to know the speaker of the quotation.

 In Act III, Scene I, Mercutio ridicules Benvolio for getting into quarrels over trivial matters:

What eye but such an eye would spy out such a quarrel?  Thy head is as full of quarrels as an egg is full of meat, and yet thy head hath been beaten as addle as an egg for quarreling.  Thou has quarreled with a man for coughing in the street, because he hath wakened thy dog that hath lain asleep in the sun.  Dist thou not fall out with a tailor for wearing his new doublet before Easter?  With another for tying his new shoes with old ribbon?  And yet thou wilt tutor me from quarreling! (15-21)

What is ironical here is that later in the scene, Mercutio--whose name suggests a mercurial personality--becomes as quickly angered in the hot temperature of the day as Benvolio has. When he feels that Tybalt insults Romeo's honor by saying, "Mercutio, thou consort'st with Romeo" (33), Mercutio retorts,

Consort!  What, dost thou make us minstrels? An thou make minstrels of us look to hear nothing but discords.  Here's my fiddlestick, her's that shall make you dance.  'Zounds, consort! (34-35)

Perhaps Mercutio's previous arguing with Benvolio, along with the temperature, has so heated him that he is thus so easily incited to anger himself.  And, despite Benvolio's second warning that they should withdraw to where they cannot be seen publicly, Mercutio throws caution away:  "Men's eyes were made to look, and let them gaze./I will not budge for no man's pleasure, I (41-42).

Here again is the motif of impetuous behavior exhibited by the youth of the play.